What is the difference between an Annual and a Perennial?

One of the most common questions from novice gardeners is the difference between an annual and a perennial.

An annual completes their life cycle in less than one year and the roots die in the winter. 

Perennials are plants that have a continuous life cycle and live for more than two years, and often many years. As the seasons change, the above ground growth dies down in the fall and new growth comes from the perennial root each spring.