What is the Difference Between a Psychiatrist and a Psychologist?

This answer reflects the situation in the United States.

A psychiatrist is a medical doctor who can prescribe medication.

Psychologists typically hold doctorates; however, they do not attend medical school and are not medical doctors. Instead, they study human thought and behavior.

Both psychiatrists and psychologists can diagnose disorders and can provide counseling and therapy; however, only a psychiatrist can prescribe medication.