WHAT IS PROXY?

A server that sits between a
client application, such as a Web
browser, and a real server. It
intercepts all requests to the real
server to see if it can fulfill the
requests itself. If not, it forwards
the request to the real server. Proxy servers have two main
purposes:
Improve Performance: Proxy
servers can dramatically improve
performance for groups of
users. This is because it saves
the results of all requests for a
certain amount of time. Consider
the case where both
user X and
user Y access the World Wide
Web through a proxy server.
First user X requests a certain
Web page, which we'll call Page
1. Sometime later, user Y
requests the same page. Instead
of forwarding the request to the
Web server where Page 1
resides, which can be a time-
consuming operation, the proxy
server simply returns the Page 1
that it already fetched for user X.
Since the proxy server is often
on the same
network as the
user, this is a much faster
operation. Real proxy servers
support hundreds or thousands
of users. The major online
services such as
America Online,
MSN and Yahoo, for example,
employ an array of proxy
servers.