See Proxy Server

a program that reads a request from a browser, forwards that request to a web server, reads the reply from the web server, and forwards the reply back to the browser

a program that usually runs on an ISP's server (or a corporate firewall/gateway) that enables users/customers to access external websites

a server that accepts all Web requests from a client and passes them along to the Web server and then accepts the response from the server and passes it back to the client

a service, based on a software such as Privoxy, that clients (i

The primary use of a proxy server is to concentrate all internal clients into a single outgoing connection. Thus the proxy will be representing all internal users towards the Internet. One popular technique is proxy caching, in which one or more computers act as a cache of documents for a set of WWW clients. These clients are configured to send HyperText Transport Protocol (HTTP) requests to the proxy. If possible, the proxy serves the requests from its cache. Otherwise, the proxy forwards the request to the content provider, that is, to the server containing the source copy of the requested data.