Today, the term is associated with the Indo-European languages known as "Tocharian". Based on a Turkic reference to Tocharian A as twqry, these languages were associated with the Kushan ruling class, but the exact relation of the speakers of these languages and the Kushan Tokharoi is uncertain, and some consider "Tocharian languages" a misnomer. Tocharian A is also known as East Tocharian, or Turfanian (of the city of Turfan), and Tocharian B is also known as West Tocharian, or Kuchean (of the city of Kucha)
The term is so widely used, however, that this question is somewhat academic. Tocharians in the modern sense are, then, defined as the speakers of the Tocharian languages. These were originally nomads, and lived in today's Xinjiang (Tarim basin). The native name of the historical Tocharians of the 6th to 8th centuries was, according to J. P. Mallory, possibly kuśiññe "Kuchean" (Tocharian B), "of the kingdom of Kucha and Agni", and ārśi (Tocharian A); one of the Tocharian A texts has ārśi-käntwā, "In the tongue of Arsi" (ārśi is probably cognate to argenteus, i.e. "shining, brilliant"). According to Douglas Q. Adams, the Tocharians may have called themselves ākñi, meaning "borderers, marchers".
The Tarim mummies suggest that precursors of these easternmost speakers of an Indo-European language may have lived in the region of the Tarim Basin from around 1800 BC until finally they were assimilated by Uyghur Turks in the 9th century AD.
A later group of Tocharians were the Kushans and maybe some Iranian tribes of the Hephthalites whose Iranian population also settled in modern Afghanistan, North-Eastern Iran, Uzbekistan, Tajikistan and Turkestan, whereas the nomadic Turkic ones were defeated by Bahram Gur and the Gok-Turks, who pushed them over the Hindukush mountains to Sindh (Pakistan) and North-West India.
The Tarim Basin mummies (1800 BC) and the Tocharian texts and frescoes from the Tarim Basin (AD 800) have been found in the same general geographical area, and are both connected to an Indo-European origin. The mummies and the frescoes both point to White types with light eyes and hair color. However it is unknown if the frescos and Tarim Basin mummies are directly connected. argue that the Tocharian languages were introduced to the Tarim and Turpan basins from the Afanasevo culture to their immediate north. The Afanasevo culture (c. 3500–2500 BC) displays cultural and genetic connections with the Indo-European-associated cultures of the European steppe yet predates the specifically Indo-Iranian-associated Andronovo culture (c. 2000–900 BC) enough to isolate the Tocharian languages from Indo-Iranian linguistic innovations like satemization.
The Tocharians appear to have originally spoken two distinct languages of the Indo-European Tocharian family, an Eastern ("A") form and a Western ("B") form. According to some, only the Eastern ("A") form can be properly called "Tocharian", as the native name for the Western form is referred to as Kuchean (see below). Commonalities between the Tocharian languages and various other Indo-European language families (as with Celtic, Germanic, Balto-Slavic, even Italic or Greek) have been suggested, but the evidence does not support any close relationship with any other family. The only consensus is that Tocharian was already far enough removed, at an early date, from the other eastern Indo-European proto-languages (Proto-Balto-Slavic and Proto-Indo-Iranian), not to share some of the common changes that PBS and PII share, such as early palatalization of velars.
Tocharian A of the eastern regions seems to have declined in use as a popular language or mother tongue faster than did Tocharian B of the west. Tocharian A speakers probably yielded their original language to Turkic language of immigrating Turkic peoples, while Tocharian B speakers were more insulated from outside linguistic influences. It appears that Tocharian A ultimately became a liturgical language, no longer a living one, at the same time that Tocharian B was still widely spoken in daily life. Among the monasteries of the lands inhabited by Tocharian B speakers, Tocharian A seems to have been used in ritual alongside the Tocharian B of daily life.
Besides the religious Tocharian texts, the texts include monastery correspondence and accounts, commercial documents, caravan permits, medical and magical texts, and a love poem. Their manuscript fragments, of the 8th centuries, suggest that they were no longer either as nomadic or "barbarian (hu)" as the Chinese had considered them.
The Tocharians, living along the Silk Road, had contacts with the Chinese, Persians, Indian and Turkic tribes. They might be the same as, or were related to, the Indo-European Yuezhi who fled from their settlements in eastern Tarim Basin after attacks by the Xiongnu in the 2nd century BC (Shiji Chinese historical Chronicles, Chap. 123) and expanded south to Bactria and northern India to form the Kushan Empire.
The Tocharians who remained in the Tarim Basin adopted Buddhism, which, like their alphabet, came from northern India in the first century of the 1st millennium, through the proselytism of Kushan monks. The Kushans and the Tocharians seem to have played a part in the Silk Road transmission of Buddhism to China. Many apparently also practised some variant of Manichaeanism.
The Atharavaveda-Parishishta associates them with the Sakas, Yavanas and the Bahlikas. It also juxtaposes the Kambojas with the Bahlikas. This shows the Tusharas probably were neighbors to the Shakas, Bahlikas, Yavanas and the Kambojas in Transoxian region.
The Rishikas are said to be same people as the Yuezhi. The Kushanas or Kanishkas are also the same people. M. A. Stein proposed that the Tukharas are same as Yuezhi. P. C. Bagchi holds that the Yuezhi, Tocharioi and Tushara were identical.. The Parama Kambojas of the Trans-Pamirs, mentioned in the Mahabharata are said to be related to the Rishikas who are placed in the Sakadvipa (or Scythia). B. N. Puri takes the Kambojas to be a branch of the Tukharas. Some scholars state that the Kambojas were a branch of the Yuezhi themselves.
Sabha Parva of Mahabharata states that the Parama Kambojas, Lohas and the Rishikas were allied tribes. Like the "Parama Kambojas" ("most distant Kambojas"), the Rishikas of the Transoxian region are similarly styled as "most distant" or "Parama Rishikas. Based on the syntactical construction of the Mahabharata verses 5.5.15 and 2.27.25, Ishwa Mishra believes that the Rishikas were a section of the Kambojas i.e. Parama Kambojas.