This document discusses psoriasis, a chronic inflammatory skin condition characterized by red, scaly skin patches. It defines psoriasis and describes its various types including plaque, guttate, flexural, pustular, and erythrodermic psoriasis. Treatment options are also summarized, including topical therapies like corticosteroids and coal tar, phototherapy using UV light, and systemic therapies such as methotrexate, acitretin, and biologic drugs that modulate the immune system. Psoriasis has no known cause but is influenced by genetic and environmental factors and commonly affects the skin of the elbows, knees, and scalp.