The audible claps that mark a taal are talis. Each clapped vibhag begins on a tali; the unclapped one begins on a khali (wave). Teen Taal, for example, has talis on beats 1, 5 and 13 — three claps, which is what its name ("three claps") refers to.
The very first tali, on beat 1, is the sam — the most important beat of all, where cycles begin and resolve. (The exception is Rupak, whose sam is a khali.)
Tracking the sequence of talis and khalis by hand is how students internalise a taal.