The labels for different mental health professionals are crazily confusing. Here's a quick summary.
Psychologists (my gang) have doctorates in psychology. They're trained in assessment and counseling/therapy. We do not prescribe medications. Some of us (not including me) do psychological testing.
Psychiatrists have doctorates in medicine. They first did generic training in medicine, then some specialized training in the psychological aspects. Some of them do a lot of counseling/therapy, but these days most of them mostly do assessment, then prescribing and monitoring of medications...and not a lot of in-depth counseling. They're great resources for anything that might be more psychological, but might be more physical. Since they have one foot in each of those camps, they can help you figure out which is causing the problems. Examples of psychological symptoms with physical causes include: bipolar, major depression, ADD/ADHD, thyroid, schizophrenia...and many others.
Social Workers have Master's degrees in social work. Some do counseling/therapy, and some do other types of social work such as working in hospitals or with stage agencies.
Counselers (Licensed Professional Counselors, or LPC's) have Master's degrees in counseling and do counseling/therapy.
Marriage And Family Therapists (LMFT's) do exactly what it sounds like. They have Master's degrees in LMFT and tend to focus on couples and families.
That's a simplistic summary to get you started. If I've slighted your professional group, let me know!
Licensed psychologist, Austin