Ogg is a free, open container format by the Xiph.Org Foundation. This format was developed for storing audio and video streams. Until 2007, OGG extension was assigned to all the files with content that used Ogg container format. Now Xiph.Org Foundation recommends to use .ogg only for Ogg Vorbis audio files.
New set of file extensions and media types was created: OGA extension is for audio only files, OGV - for video without sound, and OGX - for multiplexed Ogg.