Market equilibrium happens when supply and demand intersect at one point.
If the price is too high, we will have a surplus. ( that is more objects than needed) If the price is too low we will have a shortage. ( that is, not many objects to sell)
In either of this situations, the marketplace will work to either raise or lower the price of the object until we get to equilibrium, and the number of those willing and able to buy will be equal to those willing and able to sell.