2 kinds of "trolling"
Regular Trolling: Usually light hearted trolling. The troll is hoping for the "victims" reaction to be something like: "Oh you got me!" or something
Asshole Trolling: Usually people trying to hurt others feelings. The troll is hoping for the "victims" reaction to be something like: "LEAVE ME ALONE YOU JERK!"
EDIT: 3 kinds actually.
"Good" Trolling: Certain "Good" Trolls will troll people who are just being mean.