"Tekken Tag Tournament is the fourth installment in the popular Tekken fighting game series. It, however, is not canonical to the Tekken storyline. The game was originally available as an update kit for Tekken 3. Tekken Tag Tournament was originally for the arcade before a release to the PlayStation 2. The arcade version operated similarly, but ran on a 32 bit graphics engine like Tekken 3. It received upgraded graphics when it was ported to the home system. It, along with Tekken 4 and Soulcalibur II, was re-released in 2008 as a part of Namco Classic Fighter Collection."
Source: Wikipedia, "Tekken_Tag_Tournament," available under the CC-BY-SA License.