L indicates that the lens is an L or “luxury” series Canon lens. Such lenses are generally the best that Canon manufacture. They are marked with a characteristic red stripe around the end of the lens barrel.
Image stabilization （图像稳定系统）or IS is a Canon technology that optically corrects for camera motion when you take a photo. Since camera motion - caused by handholding the camera, for example - can result in blurring of the image at slower shutter speeds, IS can result in sharper photographs when fast shutter speeds are not possible.
Ultrasonic motors （超声波马达）do not rely on magnetic coils like most electric motors. Instead they use extremely high-frequency vibrations which translate into circular motion. The result is a very fast and pretty well silent (to human ears, anyway) lens motor. There are two basic types employed by Canon.
Image stabilization （图像稳定系统）or IS is a Canon technology that optically corrects for camera motion when you take a photo. Since camera motion - caused by handholding the camera, for example - can result in blurring of the image at slower shutter speeds, IS can result in sharper photographs when fast shutter speeds are not possible.
Ultrasonic motors （超声波马达）do not rely on magnetic coils like most electric motors. Instead they use extremely high-frequency vibrations which translate into circular motion. The result is a very fast and pretty well silent (to human ears, anyway) lens motor. There are two basic types employed by Canon.