It's power over ethernet
To the point though, never used it personally since it's not really necessary? Unless you don't have enough power plugs in your home. Generally PoE hardware is more expensive.
It's used more in big network setups, with hundreds of users where they will have PoE switches to power all their phones etc. For home use I don't really see the point.
PS. Ethernet over power, on the other hand, sounds quite cool. Then we could pay Eskom for our internet
