The relationship between demand and supply

There is an inverse relationship between the two. 

When talking about the demand for a good or service, when the demand increases and the supply is the same, the higher demand will lead to increases in prices. Alternatively, if there is a shortage of supply, with a constant demand, due to a lack of supply, naturally prices will increase as consumers out bid one another.

The same works inversely. If there was to be an over supply of products, with the demand constant, suppliers would have to lower their prices of goods and services in order to sell them. Conversely, if there was a shortage of demand, with a constant supply, suppliers would have to lower their prices in order to sell them.