I explained each of the classes to my girlfriend as she sat in front of the character creation screen for Torchlight. That's the Destroyer, he's like a big tank of a guy. Hits things with swords and axes and stuff. And that one is the Alchemist, he has magical spells and the ability to summon little imps and robots. And that one is the Vanquisher, she's good with bows and stuff. Throws traps that explode and shock people and that.
She chose the Vanquisher because it's the one with the girl character model :P