Thwack things over the head and take their money.
The brigand is an evil scout class that focuses on stuns and single target damage, and is less stealthy than many of the other scout classes. They're more about causing lots of pain in a short period of time than almost any other class in the game. They can betray into swashbucklers or vice versa, although they are a quite different class.
They're one of the better soloers in the game, as they can easily run through a chain of abilities, opening with a stealth attack, stunning, and then going around behind them for a flanking attack and then repeating until the monster is dead. They wear chain armor, so their mitigation isn't too bad at all. They dual wield and make use of poisons, so it's a good idea to bring plenty of them along with you on your adventures.
In group play, brigands focus on doing lots of damage on single targets. It's often a good idea to let the tank build up plenty of threat before unleashing attacks. If you get targeted, switching to defensive stance will often extend your lifespan considerably, as your high agility and medium armor will assist in keeping you alive. The brigand's stuns should be used liberally, particularly when you're ramping up your damage, as it cuts down on the amount of work healers have to do and makes it less important for the rest of the group to worry about threat. As such, brigands can be very useful in putting out both strong individual damage and supporting the other group members that are laying down the pain.
Brigands focus on both agility and strength, with both of them making up your total power pool. It's good to focus on both of those equally, with stamina at a distant third to increase your survivability. Some of their skills like Vicious Rake reduces the mitigation of the target to magic attacks, making the brigand helpful to classes that use those. At level 78 they even get an ability called Hood of Thugs that summons a small group of fellow brigands to beat down on his target.
Good brigands will use abilities like Stay Low to keep down their threat, as how high your threat is determines how much damage you can do safely without catching the attention of monsters. As brigands are one of the highest damage classes in the game, they'll need to pay close attention to that if they want to succeed.