You speak English, don't you?
A tag question 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".

A "tag" is something small that we add to something larger. For example, the little piece of cloth added to a shirt showing size or washing instructions is a tag.
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.

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?