What does USM mean?

USM (Ultrasonic motor) lenses are designed to focus quickly and quietly. There are three types of USM: Ring, Micro and Nano. The powerful Ring USM makes it well suited to driving large-diameter or telephoto lenses, and it also offers full-time manual focusing. It is the most widely used AF motor in the Canon EF range. As the name suggests, Micro USM is smaller and lighter, so it can be used in a wider range of lenses, while Nano USM, which was introduced in 2016’s EF-S 18-135mm f/3.5-5.6mm IS USM, is smaller still.