IDPA/USPSA "Postal Match" - what is it?

What's the story behind "Postal Matches?"

I see they've been a thing for several years but I've only recently heard of them. (Obviously I'm not very active in either sport)

Its several set stages with detailed directions. The results are then tallied nationally. The concept is everyone nationwide has one giant match.

I just did one of these. I don’t yet see where our results ended up in any grand set of results anywhere but it was fun.

Thanks. That's kinda what I guessed but I couldn't find a quick answer anywhere