Tags for an artist -- how are they determined?

Tags: #<Tag:0x00007f7d0099a910>

I just couldn’t find out this… when I list an artist (a person, a band etc.) I also get a list of tags associated with him/her, along with a count of occurence for each tag.
I cannot understand how this number is derived. I thought it would be the occurence of the tag in recordings, but I think this is not correct.
Anyone has an answer? Thank you in advance.

It’s derived from voting (counting) of MusicBrainz editors for each tag. You could add new tags or vote +1/-1 on existing. You could tag on all levels of data: