One full turn of the rhythmic wheel is an avartan. If Teen Taal has sixteen matras, then one avartan is those sixteen beats, beginning and ending on the sam.
A performance is built from many avartans stacked end to end. The artist phrases melody across them — sometimes resolving neatly at the end of each cycle, sometimes deliberately spilling a phrase across the boundary to build tension, then landing a tihai on the sam.
Counting avartans is how musicians measure form: a slow khayal may give a whole avartan to a single line of text.