Help me understand Free Jazz

So I met this lady and we were discussing music for a bit, and yesterday she sent me this:

https://www.youtube.com/watch?v=ceX_0RX3HeE (Fat Man Walks by Peter Brotzmann)

Apparently she really likes this. Now I used to think that I'm fairly well versed in non-mainstream music but I will admit that Jazz is not a type of music I'm super familiar with - to me Jazz is four black dudes in a bar in the 60s, playing Swing. You get the level of ignorance.

That said I do appreciate Mike Patton, I like the Dillinger Escape Plan and I've listend to plenty of "Math Rock" (or whatever the kids call it these days - yeah I'm old). But this piece right here has me stumped. It seems that everyone on that recording is hell-bent on preventing the noises they produce from turning into something resembling a song. Towards the end two of them stop entirely and the rest seems to actively try and annoy the audience... that, or I have no idea what's going on.

I looked Brotzmann up and he's highly regarded it seems. How can I understand what's going on in this music? What's a more "entry level" version of this? I did read up on Free Jazz on Wikipedia for now but that's not helping me appreciate what's happening. Is this serious music?