A 20mm lens is a type of wide-angle lens commonly used in photography and videography. It has a focal length of 20 millimeters, which allows for a broader field of view compared to standard lenses. This makes it ideal for capturing landscapes, architecture, and large group photos, as it can fit more into the frame without needing to step back. Due to its wide perspective, a 20mm lens can also create a sense of depth and dimension in images. However, it may introduce some distortion, especially at the edges of the frame, which can be creatively used or corrected in post-processing.