How is a request processed when entering a URL in a browser's address bar?.

When a user enters a URL into the browser's address bar, the following process occurs:

1. URL Parsing: the browser parses the entered address into parts — protocol (http/https), domain name, path, parameters.

2. DNS Query: the browser contacts the DNS server to obtain the IP address of the server by the domain name.

3. Establishing Connection: the browser establishes a TCP connection with the server using the obtained IP and port (usually 80 for HTTP or 443 for HTTPS).

4. Sending HTTP Request: the browser forms and sends an HTTP request (GET, POST, etc.) to the server.

5. Server Processing: the server receives the request, processes it (for example, calls a backend application), and forms a response.

6. Receiving Response: the browser receives the HTTP response with data (HTML, CSS, JS, images, etc.).

7. Page Rendering: the browser parses the HTML, loads additional resources, executes scripts, and displays the page to the user.

This process occurs very quickly and transparently to the user.