A pressure ulcer, also known as a bed sore or decubitus ulcer, is an injury to the skin and underlying tissue that occurs when there is prolonged pressure on the skin. This condition is most common in individuals who are bedridden or have limited mobility, as the constant pressure can restrict blood flow to the area, leading to tissue damage. Pressure ulcers typically develop over bony areas of the body, such as the heels, hips, and tailbone. They are classified into stages based on their severity, ranging from mild redness of the skin to deep wounds that may expose muscle or bone. Prevention includes regular repositioning and proper skin care.