Proxy server is a terms which means between a client computer and the Internet, and provide indirect network services to a client. 

The responsibility of a proxy server is to contact a server which is request an action and pass the response back to you.it's acts as intermediary between Server and client like a requesting machine. 

Type of proxy server : 

- Web proxy 

- Transparent proxy

- Anonymous proxy

- Distorting proxy

- Tunneling proxy

- Forward/Reverse proxy

- Open proxy