A file with the extension .M3U8 is an MP3 playlist file variation offering support for 'UTF-8 Unicode'.
'M3U' or 'M3U8' MP3 playlists are used by a variety of programs including 'Winamp' and various online radio stations, and as such are non-specific to any one program.
An 'M3U8' file is essentially a plain text file containing a list of the locations of selected media-files, instructing the chosen media player to play those specific files.
'Unicode' is an industry standard which allows computers to utilise consistently a database of other 100,000 characters, in addition to universal code charts, character properties and other related items.
'UTF-8' is the 8-bit variable length encoding method employed by 'Unicode'.