I’m listening to John Coltrane’s A Love Supreme.  If you’re into jazz even a little bit, you’re likely familiar with this one, it’s right up there with Miles Davis’s Kind of Blue.  

Any way, my question is Avant-Garde a sub-genre of Jazz or is it its own thing?   Simple as that.

Blue Train was a great album.  I’m Old Fashoned is my favorite on there!

My uneducated answer that I've come to just by experience or how I understand things (whether accurately or not).....

Avant Garde (however you spell it) was a general term that was kind of indicative of post WWII liberals or people in general (I think Europeans or the French might be where this movement kinda started) questioning all of conventional thinking (at the time, which in their minds leaned towards stuffy, uptight conservatism and there was probably some truth in that, but I use the term conservatism in a broader sense, not the same as being a conservative nowadays) on all matters of life.  But since many of them were artists, writers and musicians, it applied to their work.