HTTP Live Streaming (HLS) is an HTTP-based media streaming communications protocol implemented by Apple Inc. as part of its QuickTime, Safari, OS X, and iOS software. It works by breaking the overall stream into a sequence of small HTTP-based file downloads, each download loading one short chunk of an overall potentially unbounded transport stream.
M3U8 is a computer file format that contains multimedia playlists. A m3u8 file specifies the locations of one or more media files, rather than the video itself. Therefore, a HLS player is required to download and play the actual video files.