Yes, in internet usage, a "troll" is usually someone who posts "flamebait" to a discussion. That is, they will state something that is highly controversial in order to elicit a strong reaction to it, typically a reaction against it. They are (usually) disliked because they are seen as just stirring up arguments for the sake of stirring up arguments. Occasionally, the troll might just be trying to get someone else's hidden opinion out into the open.
"Don't feed the trolls" basically means don't take the bait, don't encourage a troll by participating in the argument they were trying to start. Not feeding the trolls is generally good advice and just good netiquette.