HTTP client firstly sends request to HTTP server. HTTP is a hypertext transfer protocol which is a request-response client server protocol. When we type a message in the address bar the URL gets converted into a request message and that message is sent to a server. The server performs any of the three functions;
1. It may interprets the request as file and keep under server's document directory and returns it back.
2. It may interprets the request as program, keeps it in server, execute it and returns the output to the client.
3. If the request is not satisfied, it returns an error message.