The name 'Tatar', also spelt 'Tartar', means 'archer' and is historically somewhat ambiguous. Over the centuries it has referred to different groups of people. Today it primarily refers to the Turkic people of the Volga region of Russia. There are three main groups of Tatars: the Volga (Kazan), Crimean and the Siberian. Formerly, Kazan Tatars would refer to themselves as 'Bolghar' or simply 'Muslim'. They are now a settled people, mainly peasants or merchants who have totally lost their traditional tribal structure.
It is most likely that the Tatars are descendants of the people called "Bulgars" who arrived in the area of the Volga in the early 8th century AD. They were well established and became a flourishing state. In the 13th century the Bulgar State was conquered by the Mongols, and it eventually became the seat of the Kazan (Tatar) Khanate. During this time it developed as a center of Islamic scholarship. Today there are an estimated 8,324,000 Tatars, the majority (7,121,000) live in Russia. Substantial colonies of Tatars have dispersed since the 1800s to live in nearly every republic of the former Soviet Union, in particular Uzbekistan and Kazakhstan. Tatars have a wide range of appearances, from fair skin and blue eyes to those resembling Mongols.
(If you ask ten Tatars "What is a Tatar?" you will receive several different answers. - Above is one.)