Psychology 
Psychology is the science  of behavior  and mental processes.  Its immediate goal is to understand individuals and groups by both  establishing general principles and researching specific cases.For many, the ultimate goal of psychology is to benefit society.In this field, a professional practitioner  or researcher is called a psychologist,  and can be classified as a social scientist, behavioral scientist,  or cognitive scientist.  Psychologists attempt to understand the role of mental functions in individual and social behavior, while also exploring the physiological 
and neurobiological  processes that underlie certain functions and behaviors. Psychologists  explore such concepts as perception,  cognition,  attention,  emotion,  phenomenology, motivation,  brain functioning, personality, behavior,  and interpersonal  relationships. Some, especially depth psychologists, also consider  the unconscious mind.a  Psychologists employ empirical methods to infer causal and correlational relationships  between psychosocial variables. In addition,  or in opposition, to employing empirical  and deductive methods,  some—especially clinical and counseling psychologists—at times rely  upon symbolic interpretation and other inductive techniques. Psychology incorporates research  from the social sciences, natural sciences, and humanities,  such as philosophy.
While psychological knowledge  is often applied to the assessment and treatment  of mental health problems, it is also applied to  understanding and solving problems in many different spheres of human activity. Although the majority of psychologists are  involved in some kind of therapeutic role (clinical, counseling, and school positions), many do scientific research on a wide  range of topics related to mental processes and behavior (typically in  university psychology departments) or teach such knowledge in academic  settings; and some are employed in industrial and  organizational settings, and in other areas such as human development and aging, sports, health, the media, law, and forensics.
source by: http://en.wikipedia.org/wiki/Psychology
