What is a Video Codec?
TL;DR: A video codec (coder-decoder) is software that compresses raw video data for storage and transmission, then decompresses it for playback. Common codecs include H.264 (most compatible), H.265/HEVC (better compression), and AV1 (newest, best compression).
Without compression, a single minute of 1080p video would be about 10GB. Codecs reduce this to 100-200MB by identifying and removing redundancy between frames and within each frame, using techniques like motion estimation and transform coding.