The front-end will transfer data to the back-end, and the back-end is directly associated with the database, so that the data from the front-end can be transferred to the database through the back-end; when the front-end requests data, it will send the request to the back-end, and the back-end will then retrieve the data from the database and transfer it to the front-end.

In practice, the browser will automatically send a file request to the backend, the backend will return the file to the front-end after processing, the front-end to receive, the browser to generate the dom tree, css tree, js tree, all created after the start of rendering. After the static interface is loaded and presented to the user, the user carries out the operation of registering and logging in, and sends the operation data (username, password) to the backend.

It is the overall thinking, the layout of the whole page (dom, css), the role of (js) as the main idea for their own processing.

Backend: come out with a single request. The main thing to do is, the front end to a request background processing the request and then make a response, and then come back again to deal with the response, the process is fixed, the difference is reflected in the processing.

Expanded:

One of the focal points of the back-end versus front-end comparison is security. In the early days of the Internet, when browsers were not secure enough and client computers had limited resources to deploy, keeping as much computation and logic as possible on the server side was the only way to ensure the stability of the application's use and the security of user-provided information.

In practice, the front-end and back-end portions of an application are now responsible for data validation, but it is highly recommended that security features and eventual data validation mechanisms be implemented on the server side so that important application components are not exposed.

For obvious reasons, event logging and code debugging are also implemented on the server side. Since the server is a process that continuously listens for requests from the client, validating legitimate requests and blocking illegal access attempts is an important part of back-end Web development.

Baidu Encyclopedia - Frontend

Baidu Encyclopedia - Backend

Baidu Encyclopedia - Database