Psoriasis is a common skin condition characterized by red, scaly skin patches that are usually found on the scalp, elbows and knees, and may be associated with joint pain and stiffness. It is caused by an immune system disorder and is influenced by genetic and environmental factors. Treatment options include topical creams and ointments, oral medications, light therapy, and management of flare-ups through control of triggers like stress, smoking, and alcohol use.