Ladies!

Can someone please explain the whole 'face sitting' thing to me please? I don't really understand it. My partner atm has asked me to sit on his face a couple times but I just don't get it, like, anything about it. If he wants to go down on me why doesn't he just do that? Instead of me being super uncomfortable in a very awkward position etc? I just don't understand and find a way out each time. He did ask if I understood what he was asking and I guess I do but don't - like I understand the kind of position he wants us in but that's literally it.

Guess I just want to get it a bit more hence asking here. Then a way to avoid ever being asked again lol, it's absolutely not for me and is such a big turn off I lose total interest in sex when asked. I don't find oral pleasurable anyway.