DTS - Digital Theater Systems - is a proprietary multichannel format developed and marketed by Digital Theater Systems. Its official name is DTS Coherent Accoustics.
It's a standard audio format in DVD, next to Dolby AC3 and LPCM. It uses considerably high bitrates, ranging around 760-1500kbps for multichannel programs. That has led some people to believe it delivers better quality than AC3, that works at bitrates up to 640kbps. Dolby retorts claiming DTS needs such high bitrates because it uses primitive and inefficient technologies for audio data reduction. A consensus on which format is better has never been established.
An Open Source DTS decoder called libdca is part of the VideoLAN project, but it was withdrawn from official public distribution because of DTS patent infringement claims.
The DTS Coherent Acoustics standard (ETSI 102 114 v1.2.1) is published by the ETSI.