EBU stands for European Broadcasting Union which is a society that develops and publishes standards for Broadcasting which are getting used around the world.
R128 is their latest standard for Loudness.
The goal of the EBU R128 standard is, that every TV Channel, Every Radio Channel, and every Video has roughly the same loudness so that the user doesn’t need to change the Volume or doesn’t get frightened by a loud Video.
This works by taking the average loudness and putting it to -23db which has been proven, to be the optimal average loudness.
In my opinion, this is one of the things which sets professionals and amateur apart.