If you've you seen John Mayer live, then you've definitely witnessed his infamous guitar face. With eyes tightly shut and lips pursed just so, he always seems to put it on when he gets onstage.

But what's the story behind that? He finally explained it to Andy Cohen on Bravo's Watch What Happens.

"I don’t mean to do the guitar face," he said on the late night talk show.

He added, "Not only [am I] lost in the music, I'm worried about falling off the bike. It's a pained sexual face."

He also talked about being honored that Khloe Kardashian included his cover of Beyonce's "XO" in her sex playlist. You can watch that convo below.