This is an exit ticket used at the end of a lesson. It gives you a quick insight on how the lesson went with your students and if you need to go back on teaching a particular part of the lesson.
They write down:
-3 new things they learned
-2 questions they still have about the lesson
-1 new vocabulary term with definition
I printed them out either 2 to a page or 4 to a page to save paper.