Why is this a turn on?

Touching and kissing you will turn him on...

What, you're expecting him to not get hard from fingering you? Guys get hard from things far less sexual than that.

No, it's not a stupid question because you're not a guy. lol! Anytime a guy does sexy stuff to a girl and he thinks she likes it, it turns him on. Your moaning helps get him turned on even more because of the possibility that you're liking it so much you might even reach an orgasm from his fingering which would mean to him that he's doing really good and that you're liking it. Whenever a guys gets turned on they get hard, and the more they get turned on the harder they get. So that's why he gets so hard because when he's turning you on he's getting really turned don too.

Era guy is different, but probably because ur moaning, I have to say that is a big turn on for me.

All guys get turned on differently.

He's turned on. Fingering you makes him horny because you're turned on and he can see that --> guys get hard when they're turned on.