EF-S stands for "Electro-Focus Short," a type of lens mount used by Canon for their digital cameras. These lenses are designed specifically for cameras with an APS-C sensor size, providing a smaller and lighter option for photographers. The EF-S lens system allows for a range of focal lengths and features, making it suitable for various photography styles, from landscapes to portraits. However, EF-S lenses are not compatible with Canon's full-frame cameras, which use the EF lens mount instead.