This essay explores the concepts of the law of demand and supply in contemporary business economics. It explains the relationship between price and quantity demanded, movement along the same demand curve, and changes in the demand curve with its factors. The essay also discusses the law of supply, movement along the same supply curve, and changes in the supply curve with its factors. Additionally, it compares and contrasts emerging theories and models in 21st-century contemporary economics with those of the 20th century and relates them to modern business practices.