Demand

 Demand is the want of customers for a specific product in market. Highest demand indicates highest need. 

Demand of product increases the supply of the product. 

For a specific types of product demand controls the price, even price also determines demand. 

Highest price lowers the demand.  But in some case highest price increases the demand.  Dress and cloths demand increases with price. 

Demand also depends on socioeconomic structure.  In a roral area a car have no demand. 

Product demand creates on its satisfying need.  In desert there may have no any demand of umbrella because there have no rain. 

Utility

 Utility is the properties of goods for which purchaser willing to pay to purchase the product.

The properties of goods that can satisfy the customer need. 

For, example the property of any laxative is to cure constipation. Hence,  it is the utility of the product.