What CAT is
CAT or Category is a standardized cable used in networking and communication. In drama we use CAT6 RJ45 Cables. RJ45 or Registered Jack 45 refers to the connectors/terminators on the cable.

An ethernet cable refers to a CAT cable with an RJ45 terminator on both ends. This is the most common connection type in networking

The latest CAT Cable is Category 8.2 which supports up to 40 GB per second transfer