Black backgrounds and such

So I’ve been reading audio reviews for 25 years but sometimes the descriptions etc used still don’t make sense or I question what they are really trying to say. What is a black background for example?  Is it the silence that exists when my system is off ?  Curious if there is some glossary or explanation or even better an audio recording which would provide examples of one descriptor vs another.  It’s kind of like wine but at least when someone says has notes of blackberry I have a reference point!