Gout is a form of arthritis characterized by sudden, severe episodes of pain, redness, and swelling, typically in the joints. It is caused by the buildup of uric acid in the blood, which forms urate crystals that deposit in the joints and surrounding tissues, leading to inflammation and intense pain. Gout often affects the big toe but can occur in other joints such as the ankles, knees, elbows, wrists, and fingers.