Some Wikipedia articles include sound or video files, that can be played on almost all personal computers. However, your computer must have the right software. If your computer does not automatically play these files when you click on them, downloading and installing free software from the Internet can enable it to do so.
Sound files on Wikipedia generally use the Vorbis audio format, and video files use the Theora format, both contained in an Ogg file. These are analogous to other formats used to play digital audio and video such as MP3 and MPEG. However, Microsoft Windows, iOS, and macOS do not support these formats by default, and require additional software to play them (see below).
Music files may occasionally use the MIDI format (.MID or .MIDI extension). MIDI is often playable without additional software, and some PCs have a MIDI-enabled player and sound card. However, for macOS (since 10.9 Mavericks), a MIDI file is not playable by both Safari and QuickTime pre-installed in the system and an alternative standalone player has to be used. The situation is similar with modern Firefox and Google Chrome browsers which do not support MIDI by default but require additional software (plugins, extensions, codecs) to play such files.
For help making and converting video and audio into the format usable on Wikipedia, see Wikipedia:Creation and usage of media files.