Question tags are short questions at the end of a statement.
These types of questions are mainly used when we want to confirm that something or when we want to find out if something is true or not.

Question tags are formed with the help of the auxiliary or modal verb of the main sentence and the appropriate pronoun.

A positive sentence is followed by a negative tag and a negative sentence is followed by a positive tag.

We usually use a negative tag with an affirmative verb, expecting the answer 'yes'.

You are coming to the party, aren't you?
Yes, I am.

We usually use an affirmative question tag with a negative verb, expecting an answer 'no'.

She doesn't like coffee, does she?
No, she doesn't.

A rising intonation on a question tag usually expresses more doubt, we are unsure of the answer and want to check information.

You know Michael, don't you? (I am not really sure, so I would like to confirm)
A falling intonation usually expresses more certainty, we are sure of the answer and expect agreement.

The weather is so nice today, isn't it? (I am sure, I want you to confirm or agree with me)

Everyone/Anyone/Someone/No one form their question tags with the help of the pronoun they

Everyone enjoyed the conference, didn't they?

Some question tags have an irregular form, e.g. aren't I, shall we

I am working overtime this week, aren't I? or I am working overtime this week, am I not?

Let's get started, shall we?

Sometimes we use an affirmative question tag with an affirmative verb to express surprise, disbelief or seeking confirmation of something unexpected.
So you did finish the project on time, did you? (the intonation is rising at the end, the speaker is surprised and is confirming something which they find hard to believe)

You really are the best at this game, are you? (the intonation is falling at the end, the speaker strongly believes in someone's abilities and emphasises it).

A positive tag with affirmative verb can be used as a request.

You could help me finish the project, could you? (the intonation is rising at the end)

We can use question tags with will, would, can and could to make imperatives sound less direct.

Pass me the salt, would you? (the rising intonation at end is used to emphasise that the speaker is making a request rather than giving a command)