RJ-45 is the standard connector utilized on 4-pair (8-wire) UTP Unshielded Twisted Pair) cable. It is generally implemented for network and telephone cabling.  Sometimes, it's also utilized for serial network connections.

The RJ-45 connector is the standard connector for 10Base-T/100Base-TX Ethernet, ISDN, T1, and modern digital telephone systems. Standard RJ-45 pinouts describe the arrangement of the individual wires required when connecting connectors to a cable. RJ-45 connectors appear similar to the RJ-11 connectors utilized for connecting telephone equipments, but they are a bit wider.

RJ-45 stands for "Registered Jack – 45".

RJ-45