>Yup,one can prescribe drugs and the other is usually on them. <
LOL! I think they're both on them.
In addition to the thoughtful comments already mentioned, a psychiatrist being an M.D. is uniquely qualified to diagnose and manage psychiatric or behavioral disorders resulting from bona fide medical conditions (schizophrenia or bipolar disorder being examples). Psychiatrists study how disorders of the body or brain affect the mind.
Psychologists are more concerned with the how the mind is affected by one's experiences, upbringing, trauma, insecurities, stresses, sociology, interpersonal relationships, etc.
If a person was sexually abused as a child, they would see a psychologist. If they have bipolar disorder, they would see a psychiatrist.