How to effectively use the Loudness Meters?

I was wondering if some of audio experts on the forum could explain how to effectively use the Loudness Meters? Especially in comparison to the regular meter.

https://www.youtube.com/watch?v=hf7QZnh4OLM

I usually just load a professionally mastered track that I think is good quality and similar in style to my own music, see what the meters are doing and then maybe try to get my track close to the same without hurting the quality of it.