A mobile app is a program installed on a smartphone or tablet that does one specific job: banking, ordering a taxi, food delivery, messaging. Unlike a website, an app sits on the phone's screen with its own icon, sends notifications and can use the phone's camera, location and storage. For a business, an app is the shortest channel of contact with a regular customer.
Key takeaways:
- A mobile app is downloaded from the App Store (iPhone) and Google Play (Android); each platform has its own rules.
- An app has three parts: the screens on the phone, a back end (server) running behind the scenes and an admin panel for the business.
- There are four main types by technology: native, cross-platform, web app and PWA.
- A website is better for finding new customers; an app is better for frequently repeated transactions with regular customers.
- Not every business needs an app: if customers buy once or twice a year, a good mobile website is enough.
What is a mobile app?
A mobile app is a program written for a phone. We use apps every day: WhatsApp and Instagram, banking apps such as Birbank, taxi apps such as Bolt and delivery apps such as Wolt.
The main things that set an app apart from a website:
- It is installed on the phone. It is downloaded from the store once and its icon stays on the screen.
- It uses the phone's capabilities. Camera, location, fingerprint or face recognition, contacts, Bluetooth.
- It sends push notifications. It can reach the user with a message even when the app is closed.
- It runs faster and more smoothly. Part of the screens is stored on the phone, so transitions are instant.
- It can partly work without internet. For example, a ticket, card or catalogue that was loaded earlier.
The market is huge. According to Sensor Tower's report, about 150 billion apps were downloaded from the App Store and Google Play in 2025, and users spent about 3.6 hours a day in apps on average (Sensor Tower). According to Apple, the App Store has nearly 2 million apps (Apple).
How does a mobile app work?
The screens the user sees are only one part of an app. Most business apps have three parts:
| Part | What it does | Who sees it |
|---|---|---|
| App (on the phone) | Screens, buttons, forms | The user |
| Back end (server) | Stores data, calculates the order, checks the payment, sends notifications | No one; it works behind the scenes |
| Admin panel | Products, prices, orders, users and reports | The company's staff |
The process goes like this: the user taps "Place order" in the app, the app sends the request to the server over the internet, the server writes the order to the database and returns a response, and a company employee sees the new order in the admin panel. This "language" between the app and the server is called an API; through the same API, the app connects to a bank's payment system, a map or a CRM.
That is why an app's value and price are determined not by the number of screens but by the complexity of the system behind them. We have shown this calculation line by line in our mobile app development cost article.
iOS and Android: what is the difference?
Almost all smartphones run one of two operating systems: Apple's iOS (iPhone) and Google's Android (Samsung, Xiaomi and other brands). Each system has its own app store: the App Store and Google Play.
In Azerbaijan, Android clearly dominates: according to StatCounter's September 2026 data, 84.33% of mobile traffic in the country is Android and 15.66% is iOS (StatCounter).
For a business this has three consequences:
- The app should be on both platforms. Choosing only one leaves out part of your customers.
- Each store has its own rules and fees. The Apple Developer Program costs $99 a year, while a Google Play account requires a one-off $25; apps go through a review before they are published.
- Two platforms do not mean twice the work. Modern technologies make it possible to write an app for both platforms from a single codebase.
We have explained the process of publishing to the stores step by step in the article how to publish an app on the App Store and Google Play.
What types of mobile app are there by technology?
Apps fall into four main types, depending on how they are built:
| Type | How it is built | Advantage | Limitation |
|---|---|---|---|
| Native app | Written separately for each platform, in its own language (Swift for iOS, Kotlin for Android) | Highest speed, all of the phone's capabilities | Two separate codebases, two teams, a higher budget |
| Cross-platform app | One codebase runs on both platforms (Flutter, React Native) | Shorter timeline and lower cost, a consistent look | Very specific features may need additional native work |
| Web app | A website that opens in a browser and works like an app | No download needed, one version works on every device | Not in the stores, limited access to the phone's capabilities |
| PWA | A web app that can be added to the home screen as an icon | Inexpensive, does not require store review | More limited capabilities on iPhone |
For most business apps a cross-platform approach is enough; native is chosen for products that need heavy graphics, complex camera work or device functions. We compare the technologies in detail in the article What is Flutter.
What is a PWA?
A PWA (progressive web app) is a web app that opens in a browser but can be added to the phone's screen as an icon. The user does not download it from a store: they open the website and choose "Add to Home Screen". After that, the PWA opens in its own window and looks like an app.
According to MDN's definition, a PWA is an app built with web technologies that provides a user experience like a platform-specific app (MDN). On iPhone, two limitations are worth knowing. First, the install prompt does not appear automatically: the user has to choose "Add to Home Screen" from Safari's share menu themselves (web.dev). Second, sending notifications has been possible since iOS 16.4, but only for web apps that have been added to the home screen (WebKit).
A PWA is a good choice when the budget is limited, the main need is a catalogue, ordering or a personal account, and being in the store is not important. If you need to be visible in the store, full notification capabilities and deep phone functions, an app is a better fit.
What types of mobile app are there by purpose?
| Type | What it does | Typical features |
|---|---|---|
| Online sales app | Sells products | Catalogue, cart, online payment, order tracking |
| Service and booking app | Books time and places | Calendar, free slots, reminders, payment |
| Loyalty app | Rewards regular customers | Bonus points, digital card, personalised offers |
| Delivery and ordering app | Delivers the order to the customer | Map, courier tracking, statuses |
| Internal app | Makes employees' work easier | Tasks, reports, warehouse, sales representative's route |
| Content and education app | Provides lessons, video and news | Subscription, progress tracking, tests |
One app can combine several types: for example, a restaurant app has ordering, reservations and a bonus system together. We explain how a bonus system is built in the article what is a loyalty programme.
Mobile app or mobile website: what is the difference?
| Criterion | Mobile website | Mobile app |
|---|---|---|
| How it opens | In a browser, via a link | Downloaded from the store |
| Found on Google | Yes | Only the store listing |
| Barrier for a new customer | None | It has to be downloaded |
| Notifications | Limited | Full |
| Phone capabilities | Limited | Full |
| Development and support cost | Lower | Higher |
| Where it works best | First contact, search, advertising | Repeat orders, regular customers |
These two channels are not rivals; they complement each other: the website brings the customer in, the app keeps them. The website comes first, and the app is built once a base of regular customers has formed. We explain what a website itself is in the article what is a website.
What does a mobile app give a business?
An app does not bring in new customers; it brings existing ones back more often. Its main benefits:
- Direct contact. A notification needs no ad budget and reaches the customer's phone directly.
- Easy repeat orders. The address, card and previous orders are remembered; the next purchase takes two or three taps.
- Loyalty. Bonuses and personalised offers keep the customer from going to a competitor.
- Data. Who buys what, and when: this data makes marketing more precise.
- Process automation. Reservations, queues and status queries are handled without phone calls.
An app pays off when the customer is in touch with you often: several times a week or a month. People do not download an app for a product bought once a year. We give a checklist for the decision in the mobile app development guide.
How is a mobile app built?
An app can be built in three ways: you assemble it yourself on a no-code platform, you rent a ready-made (white-label) solution under your own brand, or a team writes it from scratch to fit your processes. We compare the possibilities and limitations of the first route in the article creating a mobile app.
Whichever route you choose, it is safer to test the idea with a small version before spending a large budget. This approach is called an MVP, and we explain it with examples in the article what is an MVP.
What apps does Advertol build?
Advertol is an agency in Baku that builds websites, mobile and web apps and CRM systems, and combines them with marketing. Its published technology projects show the invisible but most important side of an app, namely the system behind it:
- Momento Travel. A custom CRM that collects enquiries from several WhatsApp numbers, Instagram and Facebook in a single sales dashboard; the interface works in three languages.
- AVA. Advertol's own client panel: clients follow their advertising results live.
- Padel 77. A club website where a player creates an account and books a court directly on the site.
Advertol is an agency based in Baku: website and mobile app development, Meta and Google advertising, SMM, CRM and AI automation are all run by one team. App projects are delivered under the website and app development service.
Frequently asked questions
Are a mobile app and a program the same thing?
Yes, a mobile app is a program written for a phone. "Program" is the broader word and also covers computer programs, while "app" usually refers to those for phones and tablets. In everyday speech both words are used.
Does a mobile app work without internet?
It depends on the app. A calculator or a notepad works without internet. Ordering, payment and messaging, however, require a connection to the server. A well-built app shows previously loaded data when the internet drops and updates when the connection is restored.
How do free apps make money?
In several ways: in-app purchases and subscriptions, advertising, or the app itself does not earn money but brings orders to the core business. Most business apps belong to the third group: a shop, restaurant or clinic app increases sales and customer loyalty.
Can a PWA replace a mobile app?
In simple scenarios, yes: a catalogue, ordering, a personal account. If you need to be visible in the store, make full use of notifications and have access to all of the phone's capabilities, an app is a better fit. Many companies start with a PWA and move to an app once demand has been proven.
Does an app need updating after it is released?
Yes. iOS and Android are updated every year, the stores' requirements change, and users expect bugs to be fixed. An app that is not updated will, over time, run incorrectly on new phones and may be removed from the store. That is why the support budget should be planned in advance.
Does every business need a mobile app?
No. If customers rarely buy from you and you do not need the phone's special capabilities, a fast mobile website is more cost-effective. An app pays off for businesses with frequently repeated transactions, a loyalty programme and a base of regular customers.
Conclusion
A mobile app is a program installed on a phone that uses its capabilities; behind the visible screens stand a server and an admin panel. The choice between native, cross-platform, web app and PWA depends on the budget and the features. A website brings in new customers and an app keeps them, so first look at how often the customer is in touch with you.
If you want to work out whether an app, a PWA or a mobile website suits your business, book a free strategy consultation or write to the Advertol team.