Plaque can mean two different things:
A) Dental plaque is a sticky film infested with bacteria. It hardens and forms tartar, which contains minerals and also affects tooth color.
B) Arterial plaque is a waxy, fatty substance that can accumulate on your arteries’ walls thus narrowing their internal diameter. This slows down blood flow. Arterial plaque is made of cholesterol, fibrin (a clotting agent), calcium, etc.