RJ45 - Registered Jack 45

Here RJ stands for "Registered Jack" which is a networking interface standard. There are different networking interface standards in the name of "RJ" i.e RJ11, RJ14, RJ21, RJ25 and RJ45.

RJ45 connector is the most commonly used Ethernet connector that uses 8-pins, to connect eight separate wires of the Ethernet cable. All the 8-wires has a different color out of which four are solid and four are striped. A typical RJ-45 connector looks something like this:-



It looks similar to a telephone jack - RJ11 - but it is slightly wider. The arrangement of pins in the connector made it possible for the same telephone lines to be used for transmitting data.