We use the imperative when we want to tell somebody to do something. When we use the imperative, we use only the verb.
When the imperative is negative, we use don’t.
There is also a special form of the imperative when we are a part of a group and we want the whole group to do something. In these situations, we use let’s.
We use the imperative in about 3% of sentences in spoken English.
Sit down. Come here. Bring it. Don’t jump. Don’t do it Let’s go home.
You can see more examples in the book Robinson Crusoe.