Therapy is a treatment for psychological problems in which therapists and clients work together to understand problems and come up with plans for fixing them, generally by changing ineffective thoughts, emotions or behaviors.
Personality refers to individual differences in characteristic patterns of thinking, feeling and behaving. The study of personality focuses on two broad areas: One is understanding individual differences in particular personality characteristics, such as sociability or irritability. The other is understanding how the various parts of a person come together as a whole.
Adapted from the Encyclopedia of Psychology
American Psychological Association