There is a very good chance you will never make this mistake ANYWAY, but whatever.
Okay, let me back up.
I have a not-so-secret love for shounen-ai (and shoujo-ai, if we're counting) manga (anime... not so much). I'd read in a review that there is a difference between shounen-ai and yaoi, but I disregarded it. So, after reading some cutesy shounen-ai one-shots, I found, what's it called, "Secret News." Labeled "yaoi" (and, actually, "smut," but I didn't REALLY get what that meant), I figured it would be fine. Yeah, sure, it WAS, until--
CENSORED FOR THE SAKE OF THE AUDIENCE
happened! Oh, hell, that was freaking disgusting.
Well, now I know what the difference between "shounen-ai" and "yaoi" is. Sucks how I had to find out the hard way. Maybe I should have included that on my new "Weird/or Mentally Disturbing Manga" list.
Maybe it was the "smut" label all along...
Yeah there is a huge difference between shounen-ai and yaoi but I happen to love both. I would recommend staying away from smut as it is very creepy. Sorry you learned the hard way.
Big diff between shounen-ai and yaoi. Big diff.