Ogg is a patent-free, fully open and standardised multimedia bitstream container format designed for efficient streaming and manipulation (concatenation and muxing) by the Xiph.Org Foundation.
The name "Ogg" refers to the file format which can be multiplexed with a number of separate independent open source codecs for audio, video and text (e.g. subtitles). Files ending in the .ogg extension may be of any Ogg media filetype, and because the format is free, Ogg's various codecs have been incorporated into a number of different free and commercial media players as well as portable media players from different manufacturers.
The term "ogg" is often used to refer to audio file format Ogg Vorbis, that is, Vorbis-encoded audio in the Ogg container. Other prominent Xiph codecs that are often encapsulated in Ogg are the video codec Theora, and the human speech audio compression format, Speex.