Impersonal verbs can often get people confused when learning French, but the fact is that these verbs are used in all languages including English.  Il pleut means ‘It is raining’.  These verbs are called impersonal because they can not take a real personal subject as they do not represent any action, occurence or state-of-being that can be attributed to a person, place or a thing.  In other words, although subject to dispute perhaps, no one really can come up with a personal subject that is responsible for the rain.

In French, as in English, these impersonal verbs take on the impersonal pronoun – il in our case.

Here are some examples:
1. Il neige.  (It is snowing.)
2. Il faut que tu fasses tes devoirs.  (It is necessary that you do your homework.)
3. Il y a un chien dans le jardin.  (There is a dog in the yard.)
4. Il fait beau.  (It’s nice out.)
5. Il s’agit d’une princesse qui cherche son prince charmant.  (It’s about a princess who is looking for her prince charming.)

There are some verbs that are always impersonal in French as the ones given in the examples.  We will discuss them today.

WEATHER VERBS
Il pleut, il neige, il gèle, etc.  (#1 above)
Il fait + adjective or noun (#4 above)

IL FAUT + an infinitive or noun or a subordinate clause that begins with que   (#2 above) 
Il faut un permis pour conduire.  (It is necessary to have a license to drive.)
Il faudra savoir l’addresse de ton ami pour pouvoir l’envoyer une invitation.   (It will be necessary to know your friend’s address to be able to send him an invitation.)

IL S’AGIT DE + noun or infinitive (#5 above)
Aujourd’hui il s’agit de désendetter l’économie américaine.  (Nowadays, it’s about reducing the debt of the American economy.)
Je ne vais pas te dire parce qu’il s’agit de ma vie privée.  (I’m not going to tell you because it has to do with my privacy.)

IL Y A + noun or pronoun (#3 above)
Il n’y a pas de pain.  (There isn’t any bread.)

That’s it.
Ça y est!