Instructions and warnings
Soyez bien prudents !
On doit porter un casque
Instructions and warnings are given by using the -ez ending of a verb without the vous. Grammatically, this is known as the imperative form.
An exception to this general rule is soyez... ! (be... !) which is the imperative form of être.
Il faut also tells you that you have to do something. It never changes, no matter who is talking, and can be translated in English as "you/we must" or "it is necessary to". The following verb is in the infinitive form.
Another way of saying "have to" or "must" is with the verb devoir.
nous devons vous devez ils/ elles doivent
As with il faut, the verb that follows is in the infinitive form.