What Is RJ45?
When people think of RJ45, they think of the little plastic connector at the end of a UTP cable. While 95% of people think this is correct, it technically is not.
This is actually called an 8P8C connector. This is where the 8 wires within the UTP cable terminate. For consistency, they need to be in a particular order.
There are two standards called T568A and T568B. There are plenty of diagrams, call “pinouts” available online, if you want to make your own cables.
So what really is RJ45? It was first developed as a connector for phone systems. When network cables came about, the name stuck, so many people still call them RJ45. To be honest, this is fine, because we all know what we are talking about.