Counsellor / Psychologist / Counselling Psychologist is the one who treats normal people and helps them in (1) resolving day today issues and (2) handling adverse life events. Method that Counselling Psychologist uses is Talk Therapy & his/her qualificaiton is MA / M.Sc.
Clinical Psychologist is the one who can assess, diagnose and treat people with mental disorders. Method that Clinical Psychologist uses is Talk Therapy & his/her qualification in M.Phil (RCI license)
Psychiatrist is a doctor who prescribes medication to people who are suffering with mental disorders. Psychiatrists and Clinical Psychologists often collaborate and work together to help clients suffering from disorders.