It’s a workflow concept coined by Nick Milo, or maybe he was just the one to pioneer it the most? A case for MOCs and On the process of making MOCs It doesn’t have anything specifically to do with Obsidian.
There may be plugins that try to automate it. But I think ultimately the value in it is that you are mapping out your own meaningful structure - as opposed to a Table of Contents which just lists things. And linking things in a structure is not a new concept at all. (wikis, mind maps, WWW, site maps, org charts, etc. etc. etc.) It’s just a coined name for a workflow way of thinking about it in the context of a knowledge-base.
You don’t need to know anything about it or use it or even study it. It’s just been talked about a lot in this forum since the first few months it existed (as far as I remember). That’s why it’s a popular topic around here, and that’s why it isn’t in the help docs.