A psychologist has a degree in psychology while a psychiatrist is a medical doctor specializing in mental problems. Being a medical doctor, a psychiatrist can prescribe medication, if needed. Things have changed that in some psychiatrists mainly operate as med managers. The best combination is a combination of psychotherapy and medication.
I can give an example from my own experience. When my life started falling apart I tried some counseling who referred me to a psychiatrist. I didn’t ‘click’ and looked for another and got a reference to another. I was stubborn but after no improvement I decided to try the meds that he recommended for depression. That was an improvement. But more importantly he uncovered that I had hidden anger that was the real reason for my life falling apart. Once I came to that realization my life began to improve significantly.