Functional Medicine is technically defined as: 

"medical practice or treatments that focus on optimal functioning of the body and its organs, usually involving systems of holistic or alternative medicine."

In laymen's terms, functional medicine is learning the whole person in order to achieve their best possible health. Often compared to Integrative Medicine, Functional Medicine is actually much more intensive and consequently, conclusive. While Integrative Medicine also focuses on the individual as a whole, Functional Medicine works to discover the root cause of any chronic condition from autoimmune or cardiovascular diseases to diabetes and obesity.