The ways of Tocharic migrations from Middle East to East Asia are still unknown. The languages show many borrowings from early Iranian languages, archaic Finno-Ugric and even Tibetan-like forms, but the structure itself shows much similarity first of all with Germanic and Balto-Slavic languages. Linguists think Tocharians moved through the Central Asia from the West to the East and on their way had many linguistic contacts reflected in their tongue. Before those migrations, being a dialect in Proto-Indo-European community, Tocharians must have communicated closely with future Anatolians and Italo-Celts.
Tocharian phonetics has some significant features, such as the counteropposition of firm and soft consonants, plenty of palatal and palatalized sounds like ts, c, ly, tsy and others; the reduction of unstressed vowels, especially in final syllables of the word, where both consonants and vowels could easily disappear. Tocharian B was much more conservative, and therefore preserved many archaic forms which were lost in A language.
Tocharian nominal system represented 3 genders (masculine, feminine, common - where singular had masculine, plural was feminine), 3 numbers (though dual was going to disappear), and - what is important - 9 noun cases, some of which were borrowed directly from Finno-Ugric nominal declension. Primary cases (nominative, objective, genitive) were formed from the nominative stem, other ones used the objective case stem. Endings were sometimes agglutinative, what is uncommon among Indo-European tongues.
Tocharic verbs had 3 tenses (present, future, imperfect), the 4th one is sometimes described named durative. Four moods ordinary in Indo-European languages: indicative, imperative, conjunctive, optative. One important feature of Tocharian verbs was its ability to form causative verbs from every stem, using suffixes -s-, -sk-. Verbal nouns include the participles in -l, also existing in Slavic, Armenian and Anatolian languages.
Tocharian texts written in Brahmi (or one of its varieties) were found in the beginning of this century, and already in 1908 linguists stated the language was a separate Indo-European group. But the first Comparative grammar was issued only in 1988, so the studies are still carried on very thoroughly.