We use imperative clauses when we want to tell someone to do something (most commonly for advice, suggestions, requests, commands, orders or instructions).
We can use them to tell people to do or not to do things. They usually don’t have a subject – they are addressed to the listener or listeners, who the speaker understands to be the subject. We use the base form of the verb:
Enjoy your meal.
Stop talking and open your books.
Don’t be late.
We use the imperative carefully. It is a very direct form and we don’t generally use it to make requests or commands or to give instructions.
We can use just, please or if you wouldn’t mind to make an imperative sound less direct:
Open the window a little more, please, if you wouldn’t mind.