Client part (Frontend)
The interface that the user sees in the browser. It is responsible for displaying content, interacting with the user, and sending requests to the server. Most often, the frontend is developed using HTML, CSS, and JavaScript, as well as modern frameworks (React, Vue, Angular).
Server part (Backend)
The application logic that processes requests from the user, interacts with the database, and sends back the required data. The backend can be written in different programming languages, such as Python (Django, Flask), JavaScript (Node.js), PHP, Java, or Ruby.
Database
A place to store information, such as user accounts, order history, messages, etc. Most often, relational databases (MySQL, PostgreSQL) or NoSQL storage (MongoDB, Firebase) are used.