Learn Turkish: İki tane bilet var. - There are two tickets.

In Turkish, whenever you use a number to state how many of something there are, the noun must always stay in its singular form. You say iki bilet (literally 'two ticket'), and using the plural form biletler after a number would actually be grammatically incorrect.

What is the purpose of the word tane in this sentence?

Tane is a counting word that roughly translates to 'item' or 'piece'. When counting physical objects, Turkish speakers often place tane between the number and the noun. It is not strictly mandatory here (you could just say iki bilet var), but adding it sounds very natural and common in spoken Turkish.

Why do we use var here instead of a 'to be' ending?

Var is the specific word used to express existence, meaning 'there is' or 'there are'. If you want to state that the tickets exist or are available, you state the items (iki tane bilet) and finish the sentence with var.