Is a specialized software function that serves as go-between for network clients requesting content form other servers or networks. In many respects, it is something like a traffic cop, dispatcher, and censor on a network. When a network client requests resources from an external network or perhaps an internal server, it evaluates the request using its filtering rules to determine if it should forward the request or simply drop it as unpermitted. The filtering rules are set to a particular Web address, IP address, or even a certain protocol.
-If the proxy server permits the request to proceed, it requests the resources on behalf of the client, thereby hiding the client from the external network. A proxy server can also serve as a caching server. it caches frequently requested sites and, when users request them, responds with the content without contacting the external source.