Any of the mental health professionals mentioned above can do psychotherapy. The differences are mostly in the degrees that we hold, and the focus of individuals’ practices. There is also a difference between counseling (which includes more guidance and recommendations about problems) and psychotherapy (which includes more focus on deeper issues and psychological processes). I do both counseling and psychotherapy.
I am a Licensed Professional Counselor (LPC) with a Masters degree in Transpersonal Counseling Psychology. I have trained to work with individuals and couples, and I also have expertise in depth psychotherapy, transpersonal or spiritual counseling, dreamwork, Gestalt, EMDR, and trauma therapy.
There are also music and art therapists, and there is a new field of wilderness or eco-therapy. Some counselors focus on family therapy (LMFT = Licensed Marriage & Family Therapist) or do play therapy with children. Other counselors specialize in treating addictions (CAC = Certified Addiction Counselor). Vocational, educational, and rehabilitation counselors do counseling, but not usually deeper psychotherapy.
Social workers have at least a bachelors degree to work in agencies, and a masters degree (MSW = Master of Social Work) to do psychotherapy. They are more likely to be involved in the community, and the profession has a history of assisting and advocating for poor and disadvantaged groups. Medical social workers help individuals and families navigate health care needs and services, for example, choices, options, and decisions about putting a loved one in a nursing home.
Psychologists have a doctorate, either a PhD or a PsyD. They can do psychological testing as well as psychotherapy. Some psychologists are engaged in research or teaching rather than therapy.
A psychiatrist is a medical doctor (MD) who specializes in psychiatry. Psychiatrists can prescribe medications. Most mostly focus on medication management, although some have time to do psychotherapy with patients. MDs who are General Practitioners or Family Physicians can also prescribe medications, but they may not be as up to date on interactions with medications for mental health symptoms. For example, if a doctor gives a patient an anti-depressant medication without asking about bipolar symptoms, he can put the patient at risk for a manic episode. So, especially for complex situations such as bipolar or trauma treatment, psychiatrists are preferred for their expertise in combining medications and monitoring side effects.