What is a Firewall?

What is a firewall? Firewall software is a set of related programs, located at a network gateway server, that protects the resources of a private network from users from other networks. Basically, a firewall, working closely with a router program, internet filters all network traffic to determine whether to forward them toward their destination. A personal firewall is often installed away from the rest of the network so that no incoming request can get directly at private network resources.