Every app is three parts
An app works by splitting the job across three parts. The frontend is everything you see and touch (screens, buttons, forms. The backend is a program running on a server somewhere, doing the thinking) checking passwords, applying rules, processing payments. The database is where everything worth remembering lives, accounts, orders, messages.
The frontend lives on your phone; the backend and database live in a data center. They talk to each other over the internet through an API: effectively a menu of requests the backend agrees to answer, like “log this user in” or “fetch these orders”.
That is genuinely the whole architecture. Instagram, your banking app and a humble booking tool differ in scale and polish, not in shape.
What happens when you tap a button
Take something ordinary: you open a food delivery app and tap “reorder”. In the second that follows:
- The frontend wraps your request (who you are, what you tapped) and sends it to the API.
- The backend checks your identity, pulls your last order from the database, confirms the restaurant is open and prices are current, creates the new order, and triggers the payment.
- Other services get looped in: the payment provider, a notification to the restaurant, a confirmation to you.
- The response comes back and the frontend redraws the screen: order confirmed, 35 minutes.
Round trip: under a second, usually. When an app feels slow or flaky, one of these steps is struggling, which is why “just make the app faster” can mean anything from compressing images to re-architecting a database. The diagnosis matters more than the demand.
Native, web or hybrid: the same parts, different wrappers
The three-part shape stays constant; what varies is how the frontend is built and delivered.
- Native apps are built specifically for iPhone or Android and installed from the store. Best feel and deepest device access (cameras, notifications, offline) at the highest cost, often two codebases.
- Web apps run in the browser: nothing to install, one codebase, instant updates. We covered these in depth in web app development.
- Hybrid and cross-platform apps write one codebase that ships to both stores. The pragmatic middle for most business apps.
The choice is a budget-and-audience decision, not a technical beauty contest. An internal tool for staff rarely justifies native development; a consumer product living on push notifications often does.
Why this matters when you are paying for one
Once you know the parts, app quotes stop being mysterious. “A simple app” is never one thing, it is a frontend (every screen designed and built), a backend (every rule implemented and secured), a database (designed, backed up, kept private) and the connections between them (built, tested, maintained).
- Features multiply across parts. “Add user accounts” touches all three parts plus security. That is why small-sounding features carry real price tags.
- The backend is the iceberg. Buyers judge apps by screens, but most engineering effort, and most ongoing cost, lives in the part nobody sees.
- Maintenance is structural. Operating systems update, security patches land, servers run monthly. An app is a small ongoing operation, not a one-off purchase.
A useful question for any app quote: which of the three parts does this feature touch? If the answer is “all of them”, the price is honest.
Do you actually need an app?
Honest answer: sometimes no. If the goal is being found and enquired with, a fast website does that job at a fraction of the cost. If the goal is automating an internal process, workflow automation often replaces the app you thought you needed. The cases that genuinely justify an app: recurring logged-in use, offline or device features, or software that *is* the product.
If you are weighing it up, our app development guide covers scoping and costs, and our app development team is happy to tell you if a website or an automation would do the job for less. We would rather lose a scoping call than build you an expensive answer to the wrong question.
Frequently asked questions
What are the main parts of an app?
Three: the frontend (the screens and buttons on your device), the backend (a server program that applies the rules and does the processing), and the database (where accounts, orders and content are stored). They communicate over the internet through an API.
What is an API in simple terms?
A menu of requests one program agrees to answer for another. When an app’s frontend needs something (log in, fetch orders, process a payment) it sends a request to the backend’s API and gets a structured answer back. APIs also let your app talk to outside services like payment providers and maps.
Why do apps need the internet to work?
Because the thinking and remembering usually happen on a server, not on your phone. The device shows the interface; the backend and database it talks to live in a data center. Some apps cache data to work offline temporarily, then sync when the connection returns.
What is the difference between a native app and a web app?
A native app is built for a specific platform and installed from an app store, best performance and device access, highest cost. A web app runs in the browser with nothing to install and one codebase to maintain. Hybrid approaches ship one codebase to both stores as a middle path.
Why does app development cost so much?
Because every feature spans multiple parts: screens on the frontend, rules and security on the backend, structures in the database, plus testing across devices. The visible interface is a fraction of the engineering. Ongoing costs (servers, updates, security patches) continue after launch, which honest quotes include.