What is Tag Management?

Doesn't tell me what tag management is, just an advert.

'Tags' is quite possible the worst possible name marketers could have used for the need for implementing these event driven snippets. When it comes to html and websites, 'tags' should never NOT mean literal html tags.

unfortunately, i didn't understand a word of it.
what the fuck is this shit?
is it some advertising crap that I block anyway?