m3u8 如果简单理解成 mp3 的一个播放列表，「视频分片」的概念就很清晰了：
M3U (MP3 URL or Moving Picture Experts Group Audio Layer 3 Uniform Resource Locator in full) is a computer file format for a multimedia playlist. One common use of the M3U file format is creating a single-entry playlist file pointing to a stream on the Internet. The created file provides easy access to that stream and is often used in downloads from a website, for emailing, and for listening to Internet radio.
The Unicode version of M3U is M3U8, which uses UTF-8-encoded characters. M3U8 files are the basis for the HTTP Live Streaming (HLS) format originally developed by Apple to stream video and radio to iOS devices, and which is now a popular format for Dynamic Adaptive Streaming over HTTP (DASH) in general.
The current proposal for the HLS playlist format uses UTF-8 exclusively and does not distinguish between the “m3u” and “m3u8” file name extensions.
然后这项技术是 Apple 研究出来的，一种基于 HTTP 的视频流：
HTTP Live Streaming (also known as HLS) is an HTTP-based adaptive bitrate streaming communications protocol developed by Apple Inc. and released in 2009. Support for the protocol is widespread in media players, web browsers, mobile devices, and streaming media servers. An annual video industry survey has consistently found it to be the most popular streaming format.
HLS resembles MPEG-DASH in that 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. A list of available streams, encoded at different bit rates, is sent to the client using an extended M3U playlist.
今年（2019年）苹果发布了 Low Latency HTTP Live Streaming 是这项技术的进一步拓展：
