A question tag is a special construction in English. It is a statement followed by a mini-question. The whole sentence is a "tag question", and the mini-question at the end is called a "question tag".

We use tags in spoken English but not in formal written English. They are not really questions but are a way of asking the other person to make a comment and so keep the conversation open.

Making a tag is very mechanical. To make a tag, use the first auxiliary. If there is no auxiliary, use do, does or did. With a positive sentence, make a negative tag and with a negative sentence, make a positive tag..

The basic structure is:

Statement Question Tag
+
Positive statement,
-
negative tag?
Snow is white, isn't it?
-
Negative statement,
+
positive tag?
You don't like me, do you?
We use tag questions at the end of statements to ask for confirmation. They mean something like: "Am I right?" or "Do you agree?" They are very common in English.

Notice that the question tag repeats the auxiliary verb (or main verb when be) from the statement and changes it to negative or positive.