Uhhh... So basically you fight mobs, bosses, other players, and you can either be a Mage (staffs, wands, magic, healing), Warrior (swords, shields, maces, hammers), or Hunter (bows, daggers, tricks, stealth). There's also subclasses that branch of of these groups:
Mage: Warlock (basically magical leeches), Cleric (the medics), Sorcerer (elemental magic)
Warrior: Berserker (uses 2 humongous swords and smashes enemies), Knight (swords and shields), Paladin (hammers and use healing powers)
Hunter: Trickster (kind of self-explanatory), Ranger (archers), Assassin [for edgy people (jk you can choose assassin if you want)]
It's still in beta so it's going to be a pretty big game once it's done