There's a lot of them

From "highest on the pecking order to lowest"
Psychiatrist -- These are MD's or DO's who first complete medical school, then do 3-5 years of specialized training in performing therapy, testing, ECT, and other mental health areas.
Psychologist -- These are Ph.D.s in Psychology who then attend 1 addtional year of internship. They generally do testing and therapy.
Clinical Social Worker -- LCSW or BCSW. These are Master Degree social workers who then undergo 2 additional years of supervised training. They perform group and individual therapy
LPC -- Licensed Profesional Counselor, holds a Master's degree in Psychology.
LMFT -- Licensed Marrige & Family Therapist, hold's a master's degree usually in an educational or family field.
Other -- Religious/spiritual counseling, Bachelor's and Master's degree's w/o the required additional training, etc.