What is the theka of teental?

The theka of Teental (meaning the rhythmic framework or skeletal structure) is a 16-matra cycle. There's no single "correct" way to write it out, as variations exist depending on the gharana (school of musical style) and individual artist's preferences. However, a common representation uses bol (percussion syllables) like this:

Dhin dha dhin dha dhin dha dhin dha | dha dhin dhin dha dhin dha dhin dha

This represents the sixteen matras, with the "|" indicating a slight caesura or break in the flow, often but not always present in performance. Different gharanas might place the emphasis slightly differently, or use slightly different bol combinations to express the same underlying rhythmic structure.