A cyst is a closed, sac-like structure that can form within tissues and is typically filled with fluid, semi-solid material, or air. Cysts may develop in various parts of the body, including the skin, ovaries, kidneys, breasts, or other organs, and are often benign and painless. They can result from blocked ducts, infections, inflammation, genetic conditions, or injury. While many cysts cause no symptoms and resolve on their own, some may grow larger, become infected, or cause discomfort depending on their location. Diagnosis may involve physical examination or imaging studies, and treatment ranges from simple monitoring to drainage or surgical removal if the cyst becomes painful, persistent, or complicated.