A supply schedule is a table indicating various quantities at alternative prices. A supply curve is a graphical representation of the relationship. Everything, other than the price, that affects the quantity produced is held constant. In the market for apartments this would include construction technology, the prices of land, labor and materials, the alternatives available to landlords, etc. Interpreting supply schedules and curves.
Supply represents a boundary for consumer behavior.
At a given price, supply indicates the most that would be produced. To increase the quantity produced, the supply price increases. The interaction of supply and demand determine the price. There is no central direction. An equilibrium is a state of rest, there is no tendency or pressure for change.