Expansion or contraction in quantity supplied (movements along the supply curve)
When the supply of a good increases as a result of increase in its price, we say there is an expansion in the quantity supplied which leads to an upward movement on the supply curve. When supply of a good decreases as a result of decrease in its price, we say there is a contraction in the quantity supplied, which leads to downward movement on the supply curve. It can be shown in the form of a diagram:
Earlier price was OP and quantity supplied was OQ. When price increases to OP2, quantity supplied also increases to OQ2. And similarly when price decreases to OP1 quantity supplied also decreases to OQ1. Both expansion and contraction could be shown on the same supply curve. Hence it is called as movement on the supply curve.