The layer of cells that covers surfaces in your body is called epithelium. Epithelial tissue can be found lining organs, glands, and body cavities, forming a protective barrier between internal structures and the external environment. This tissue plays several critical roles, including absorption, secretion, sensation, and protection from pathogens. Epithelial cells can vary in shape and arrangement, leading to different subtypes like simple or stratified epithelium, depending on their thickness and cell organization.