Proxy server is a computer system or router that called as "proxy," .It breaks the connection between sender and receiver. Functioning as a relay between client and server, proxies are help to prevent an attacker from invading the private network. 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.
An advantage of a proxy server is that its cache can serve all users. If one or more Internet sites are frequently requested, these are likely to be in the proxy's cache, which will improve user response time. In fact, there are special servers called cache servers. A proxy can also do logging. The proxy server can limit what Web sites users on the network can access. Many organizations choose to block access to sites with objectionable material such as hacking information and pornography, but other sites can be filtered as well.