These evil creatures were once elves, twisted and tortured by Morgoth to become his vicious and mean servants. They're stronger and tougher than your average human, but also uglier and more stupid. A single orc is not very dangerous, but this isn't really very relevant since they almost always appear in large groups. However, an experienced fighter shouldn't have any trouble with even a large number of orcs; only their numerous uniques might actually give some challenge to them.