Poe is very, very physically and verbally affectionate. It comes as a second nature to him, so pet names/compliments and small touches like hugs, an arm around the shoulder or hand-holding are something he does without thought.

Finn has no idea what to do because he's never been treated like this and he loves it and craves all the attention Poe's giving him, but he doesn't know if Poe is doing it out of friendship or romantic interest and it's driving him crazy.