A keyframe, also called an I-frame or intra-coded frame, is a complete video frame in a compressed stream that contains all the image data needed to reconstruct the picture without reference to any other frames. In between keyframes, the video stream stores only the differences between frames rather than full images, which is how compression achieves small file sizes. Keyframes are essential reference points for stream recovery, so their frequency affects how quickly a stream recovers after packet loss.