TTT is an approach to grammar teaching used when the students probably already have some familiarity with the target language. First, the teacher gives students an activity to test (check) how well they know it. S/he then teaches the parts students don't know or can't do well. Finally, students' understanding is tested (checked) again in another activity.

Here test does not mean a formal exam.

Confusingly, TTT is also used to stand for

1. 'Teacher talking time.' This refers to the amount of time the teacher spends talking in a lesson.

2. 'Topic, task, tools' - mnemonic for the things you need in order to devise a successful speaking lesson.