There’s no real difference between websites and apps.
First of all, "app" is short for "software application." It’s not exclusive to mobile apps. For instance, WrongPlanet is a web app because it runs in a browser. If Alex had the time and energy, he could create a mobile app for WrongPlanet and publish it on Google Play or the App Store. It would still display the same threads and information.
For some reason, people often refer to mobile apps specifically when they say "app," but that’s a common misconception.
What’s the difference, for example, between the Facebook app and the Facebook website? Or the LinkedIn app and the LinkedIn website?
The only difference is in how the content is displayed and how users interact with it. Both the app and the website pull data from the same source.
You could even access Facebook on a smart TV—it would still show the same data. The only difference is that you’d interact with it using a remote control instead of a mouse, keyboard, or touchscreen.
### Technical Details
Any app, whether it’s a web app or a mobile app, generally consists of three layers:
1. **The Client App (Frontend):** This is everything you see and interact with. It runs in a browser, on a desktop, or on a mobile device.
2. **The Backend App:** This runs on servers. It handles requests from the client, such as fetching data from a database or updating records based on user actions.
3. **The Database:** This is where all the data is stored, including user profiles, credentials, messages, and other content.
This basic structure applies to simple apps like a to-do list, but large digital services have much more complex infrastructures. They often include caching servers for faster data retrieval, file storage systems, multiple databases for different types of data, load balancers, and other components to handle high traffic and ensure reliability.
### Multiple Client Apps, One Backend
It’s important to note that multiple client apps can interact with the same backend. This means a service can have a website, an Android app, an iOS app, and even a desktop app—all of which connect to the same backend and database.
### A Concrete Example: OkCupid
OkCupid started as a website. Its client app was written using technologies like HTML, CSS, and JavaScript. The backend was likely built with a server-side language such as PHP, Node.js, Go, Java, or something similar.
When OkCupid decided to develop a mobile app, they didn’t have to rewrite everything from scratch. They simply created new client apps—one for iOS and one for Android (or possibly a cross-platform app using technologies like React Native or Flutter). The backend remained largely the same, and the data in the database didn’t need to change.
Both the "app" and the "website" connect to the same backend, access the same data, and provide the same core functionality. The main differences lie in how the user interface is designed and how users interact with the service on different devices.