Orcs come in four types:

The Orc, Sergeant and Warlord are melee oriented. The major difference is in the number of hit points. Of course, the harder they are to kill, the more and better treasure they have. The Orc Shaman is another case entirely. If given the chance, they’ll toss a couple of ranged spells at you and then close to melee. If that’s not possible, they’ll turn invisible and try to get you by surprise. If you can see them turn invisible, start swinging in that direction and they’ll walk right into it (no one ever claimed that orcs were terribly bright). Treasure for all four is usually armor, weapons and money.