In network terminology a port can refer to a physical jack. Particularly, it can refer to the many jacks on a switch or repeater. For example, an "8 port ethernet switch" is a switch with 8 ethernet jacks.
Alternatively, ports are used by the UDP and TCP protocols to multiplex. Each host running IP has 65536 UDP ports and 65536 TCP ports. Data transfers occur between the IP address and port of one host to the IP address and port of another host. Servers will listen on special well-known ports. Clients will allocate ephemeral ports, and send data to the server's well-known ports from there.
As an aside, IP does not have links. IP and UDP are both connectionless protocol. TCP, however, is a connection-oriented protocol and does establish links.