The mandible (jawbone) is controlled by the four muscles of mastication (chewing).
The four muscles and their actions are:
temporalis: elevates and retracts the mandible (you can feel this by clenching your closed jaw and putting your hands on the sides of your head)
medial pterygoid: elevates mandible and allows for lateral movement (move your jaw side to side)
lateral pterygoid: protracts the mandible (push you chin forward to feel this movement)
masseter: also is involved with elevating and retracting.