A proxy server is a server that retrieves data out on the Internet such as a web page on behalf of a user. For example; normally when a computer wants to view a web page out on the internet, you would just open up a web browser and then type in the address.
It retrieves that web page from its web the server now when you go through a proxy server the proxy server will act as a middleman and to retrieve that web page for you.
This way, the proxy server receives the request from your computer and the proxy server will directly retrieve the web page on your behalf and then send it to your computer.
A proxy has several benefits and one benefit is privacy because it allows you to surf the internet anonymously because it hides your IP address because without using a proxy and when you visit a website your public IP address is visible so certain people can know which websites you're visiting - but when you use a proxy your IP address becomes invisible.
It happens because as the proxy server is retrieving the webpage for you only the IP address of the proxy server can be seen viewing the webpage so your IP address stops here and then the proxy IP does the rest of the work
Another benefit of using a proxy server is speed. For example if a company uses a proxy server and whenever a user wants to retrieve a webpage the proxy server will retrieve the webpage from the Internet on behalf of the user.
Once it retrives the data, It'll store that web page into a centralized cache database so if another user on a different computer goes to a webpage that has been stored in the proxy database the proxy server doesn't have to go out on the Internet to retrieve the web page it can simply retrieve it from its database and then send it to the user so this makes webpage retrieval much faster.