Market equilibrium happens where supply equals demand (supply curve intersects demand curve). An equilibrium implies that there is no force that will cause further changes in price, as quantity exchanged in the market. This is analogous to a cherry rolling down the side of a glass; the cherry falls because of gravity and rolls past the bottom due to momentum, and continues rolling back and forth past the bottom until all of its' energy is expended and it comes to rest at the bottom - this is equilibrium [a rotten cherry in the bottom of a glass].