Glossary / Backend
What is the backend?
The backend is the behind-the-scenes part of an app that users never see: the server code that applies the rules, talks to the database, keeps secrets and connects to other services.
When you press "Book" on a booking page, the frontend sends the request to the backend. The backend checks the slot is still free, saves the booking in the database, sends a confirmation email, and tells the frontend it worked.
The backend is where trust lives. It decides who is allowed to see or change what, it holds keys for services such as payments and email, and it checks every request rather than believing what the browser says.
Backends run on servers or serverless platforms, and talk to the frontend through an API.
Questions
Can an app work without a backend?
Simple ones can, such as a static website or a calculator. Once you store data for many people, take payments or need private keys, you need a backend.
What is backend-as-a-service?
It is a ready-made backend, usually a database plus sign-in and storage, that you use instead of writing your own server.