A simple epithelial tissue is an epithelial tissue which possesses a single layer of tissue cells.
Simple epithelial tissues are do not densely buffet extracellular materials and are most commonly found in areas that materials frequently need to permeate. This means places where absorption or secretion rates are high tend to have simple epithelial tissues, such as the lungs or the intestine.
A pseudostratified epithelial tissue is still categorized as a simple epithelial tissue.