Tatars (Old Turkic tatar; modern Volga Tatar: Татарлар, Tatarlar تاتارلار ), historically Tartars, is an umbrella term for Turkic peoples in the territory of the former Russian Empire (and as such generally includes all Northwestern Turkic speaking peoples).
The Tatars formed the Turkic-speaking population of Tartary, the lands ruled by Mongol elites from the 14th century until the conquests of the Russian Empire in the 18th to 19th centuries. During the early modern period, a distinction was made between the European and Asian Tatar territories, by referring to Lesser Tartary and Greater Tartary, respectively.
The largest group by far that the Russians have called "Tatars" are the Volga Tatars, native to the Volga region (Tatarstan and Bashkortostan), who for this reason are often also simply known as "Tatars", with their language known as the Tatar language. As of 2002 they had an estimated population close to 6 million.
Besides the Volga Tatars, there are smaller groups of Turkic-speaking Muslims also still referred to as "Tatars". The largest group of these, the Crimean Tatars, number close to half a million; their Crimean Tatar language is intelligible to the Volga Tatars.
Tartars were a collection of nomadic Turkic peoples of Eastern Europe and Central Asia. While mostly Muslim, some tribes were Christian or Buddhist. With the expansion of Russia and later the Soviet Union, Tartars were mostly forced to give up their nomadic lifestyle and became farmers. However, the formation of the CoDominium and the establishment of the Bureau of Relocation led to the involuntary deportation of some tribes and clans to planets such as Haven. In the more primitive societies on such planets, Tartars reverted to their nomadic ways.