Computers are identified on a network –-either LAN or the
Internet—by means of an IP address. Computers or the applications
installed on them communicate with each other through communication
ports.
There are two types of ports: TCP and UDP. In order for certain applications to operate correctly, sometimes it is necessary to open, in the firewall, the ports used by these applications. As a general rule, the documentation accompanying these applications includes information about the ports they use and which will therefore need to be opened in the firewall. You can open specific ports in the firewall by creating customized connection permissions for any of the installed programs you choose.