In sentences like ‘Come here’, ‘Sit down’ and ‘Don’t worry’, the verb forms come, sit and don’t worry are called imperatives.

Affirmative imperatives have the same form as the infinitive without to. Negative imperatives are constructed with do not +infinitive.

Imperative sentences are used to make suggestions, give advice or instructions. They are also used to tell or ask people what to do.

Don’t lean out of the window.
Tell him I am not free this evening.
Have a nice day.
Enjoy your holiday.

Note that imperatives followed by and or or can have similar meanings to if-clauses.

Shut up or I will hit you. (= If you don’t shut up I will hit you.)
Walk down our street any day and you will find kids playing. (= If you walk down our street any day you will find kids playing.)

Emphatic imperatives
Emphatic imperatives are made with do + infinitive. This is common in polite  requests, complaints and apologies.

Do sit down.
Do forgive me.

Subject with imperative
An imperative sentence does not usually have a subject, but sometimes we use  a noun or a pronoun to make it clear who we are speaking to.

John come here.
Somebody open the door.
Nobody move.

You, when used before an imperative, suggests anger or persuasion.

You take your hands off me!

Question tags
The question tags after imperatives are will you? won’t you? would you? can you? can’t you? and could you? After negative imperatives will you? is used.

Sit down, won’t you?
Be quiet, can’t you?
Don’t tell anybody, will you?