1.      Meaning
Demand is a desire backed by ability to pay and willingness to buy a given price for a commodity at given time and place.

2.      Origin and Purpose
Demand originates form the consumers who want to satisfy their wants.

3.      Price Relationship
There exists an inverse relationship between price and demand. It means that more quantity is demanded at lower price and vice versa.

4.      Shape of the curve
Demand curve slopes down ward from left to right. Demand curve has a negative slope.

Supply refers to the quantity of a commodity offered for sale at a given price and at a given time and place.

Supply originates from the producers/sellers/dealers who want to earn profit.

There exists a direct relationship between price and supply. It means that more quantity is supplied at higher price and vice versa.

Supply curve slopes upwards from left to right. Supply curve has a positive slope.