This tense is much like the present tense for many verbs. It is how we give an order or a command in French. Like the English version, the subject pronoun is omitted when giving an order and the only people you can give an order to are those people you are speaking to, whether that be one person or a group or a group including yourself. That is why it is only conjugated with Tu, Nous and Vous.
ER verbs
The only difference with the present tense is that with “tu” - the “s” is dropped
RANGER - to straighten up
Tu Nous Vous
range rangeons rangez
ÉCOUTER - to listen
Tu Nous Vous
écoute écoutons écoutez
IR and RE verbs
Most IR and RE verbs don't change at all. This includes (believe it or not,) the verb faire.
SORTIR - to exit
Tu Nous Vous
sors sortons sortez
METTRE - to put
Tu Nous Vous
mets mettons mettez
IRREGULAR verbs
The two most commonly used irregular verbs, when giving an order are être and aller (and aller doesn't change that much. It just drops the "s" on "tu").
ÊTRE - to be
Tu Nous Vous
sois soyons soyez
ALLER - to go
Tu Nous Vous
va allons allez
Some examples:
Ferme la porte! - Close the door!
Venez-ici! - Come here!
Allons-y! - Let's go!
Soyez tranquilles! - Be quiet!
If they are reflexive verbs, the object pronoun follows the imperative verb with a dash in between the two.