I assume you are not a technical person , so I will try to give the answer using as few technical words as possible. When you ( user) type the address of a website from your browser ( client) and press enter button , then according to the address given by you, the browser will go to that address with your request and request the server to enter the subject matter (what is the server below). Different guys). After receiving the request, the server looks for it in the database. If the information you requested is found according to the URL you provide , the server sends the information to your browser ( response) . The manner in which such conversations between browsers and servers take place is expressed in accordance with certain protocols of the Hypertext Transfer Protocol ( HTTP) . In this protocol or method the server gives different types of answers which can be divided into 5 parts - 1. 1xx ( Request accepted or processed ) 2xx successfully delivered or successfully delivered) 3. 3xx ( requires more steps to complete the request) 4. 4xx ( no forgotten user request completed) 5. 5xx ( Server failed to answer correct request) The value of xx can be any value 0-9. For example, your 404 or 404 error is basically 4xx error of 4 where it was not found according to the given address . Thus this series has more error codes , such as - 400, 401, 402, 403 etc. In the case of other series also the answer code with 3 numbers or response code is sent to the browser as server answer. * Server - A computer that is always connected to a network so that the client ( browser etc.) can actually answer any request. It contains various files such as PDFs , song files , web pages or html files.