Pack Leader:
The pack leader is the male head of the pack. He is the strongest male in the pack, and inspires the respect, or fear, of the rest of the pack.
Responsibilities - The Pack Leader is in charge of making sure the pack is safe. He must lead them wisely, and keep away anything that threatens the pack. Any wolf that wishes to join the pack, or move into the territory, will be approved or rejected by the pack leader.
Peace Keeper:
Generally the mate of the pack leader, the peace keeper is the strongest female in the pack. She also plays the role of pack deputy, taking over leadership of the pack if, for whatever reason, the pack leader is unable to lead. It is rare for the peace keeper to overthrow the pack leader and become the head of the pack, but it's been known to happen.
Responsibilities - The Peace Keeper, as her name implies, keeps the peace in the pack. She sorts out any fights between pack members quickly, and is in charge of all of the pack's hunting. She also acts as adviser to the pack leader and needs to be ready to temporarily take over command of the pack if the pack leader is, for whatever reason, unable to.