Question tags are short questions added to the end of statements to ask for confirmation or agreement. There are different question tags used depending on the tense and structure of the main clause, including changing the order of subjects and auxiliary verbs. Common question tags include "isn't it?", "don't they?", "won't you?", and "shall we?". The document provides examples of question tags used with statements containing different verbs tenses, including present, past, continuous, perfect, modal and future verbs.