[#] A Firewall is a network security system designed to prevent unauthorized access to a private network from any other network. It works closely with a router program to determine if a packet should be forwarded to its destination. It also provides a proxy service that makes network requests on behalf of the users on a network.
[#] All Traffic between the network and the internet in either direction must pass through the firewall. The Firewall decides if the traffic can be allowed to flow, or weather it must be stopped from proceeding further.Technically, Therefore a firewall is a specialized version of a router. Apart from the basic routing functions and rules. a router can be configured to perform the firewall functionality with the help of additional software resources.