Question

I am confused on when I can use the 3 cases.

Thanks

Answer 1

C'est/ Ce sont                                                     Il est, Elle est, Ils sont, Elle sont

C'est beau / it's beautiful                                     Il est beau / He's beautifulil

C'est Pierre, c'est le gérant or il est le gérant        That is Pierre, he's the manager 

When teaching to spanish community I say that:  

C'est is use to present and il est is use to describe but... C'est can be use to describe as well if you use an article like un, une la, le or possessive adjective like mon, ma, ton ta, notre,  

The woman over there is Michelle, She's my boss, she is very kind 

La femme là-bas c'est Michelle, c'est ma patronne, elle est très gentille

 

From About.com

The French expressions c'est and il est are extremely important impersonal expressions. They can mean things like this is, that is, it is, they are, and even he / she is.

Paris ? C'est magnifique !  Paris? It's magnificent!

Il est facile d'apprendre le français.   It's easy to learn French.

C'est une fille sympa, Lise.              Lise? She's a nice girl.

Où est Paul ? Il est en retard.        Where's Paul? He's late.

C'est and il est are the root forms, used for impersonal expressions and general comments: It's interesting, It's nice, It's fortunate, It's too bad, etc.

When talking about specific people, things, or ideas, c'est and il est may change.

• C'est becomes ce sont when followed by a plural noun. In spoken French, though, c'est is often used anyway.
• Il est becomes elle est, ils sont, or elles sont, as appropriate depending on the gender and number of the noun that it is replacing or modifying.

Ce sont des Français ?  Non, des Italiens.                 Are they French? No, Italian.

Voici Alice - elle est professeur.                               This is Alice - she's a teacher.

Despite their similar meanings, the expressions c'est and il est are not interchangeable - there are rules for using each one. The following table summarizes the different things that can be used after each of them. Click the links in the red box below for detailed information about each of these uses of c'est and il est.

IL EST  C'ESTAdjective describing a person
Il est fort, cet homme.
(That man is strong.)
Elle est intelligente.
(She is smart.)vsAdjective describing a situation
J'entends sa voix, c'est bizarre.
(I hear his voice, it's weird.)
C'est normal !
(That's normal!)Unmodified adverb 
Il est tard.
(It's late.)
Elles sont ici.
(They are here)vsModified adverb
C'est trop tard.
(It's too late.)
C'est très loin d'ici.
(It's very far from here.)
Il est avocat.            C'est un bon avocat
(He's a lawyer.)         (He's a good lawyer)

Elle est actrice.
(She's an actress.)
C'est un avocat.
(He's a lawyer.)

C'est une bonne actrice.
(She's a good actress.)

 
Il est à la banque.
(He's at the bank.)

Elle est en France.
(She's in France.)
Proper name
C'est Luc.  (That's Luc.)
C'est moi.  (That's me.)
 

Hope it will help

À la prochaine

Yanick

Answer 2

 

"il faut" is a way to express obligation, it's impersonal... It comes from the impersonal verb "Falloir" which can only be use with the singular third person "il". Beside the verb  "falloir"  you would use the verb "Devoir" to express any obligation.

Usually the structure is like this : Il Faut   +   infinitive form of a verb

Il faut manger avant la compétition = it is necessary to eat before the competition

And on a more advance level the structure could be : Il faut que + subjunctive form of a verb

 

Form the web page "Linguee" I wrote il faut and some of this example came out.

pour prendre des décisions communes, il faut écouter et respecter chacun,  (If we are to take joint decisions, we must listen to and respect every one,)

Il faut notamment évaluer rapidement, selon divers scénarios, les conséquences hydrologiques de ce changement. (It is especially necessary to quickly assess the hydrological consequences of this change, according to various scenarios.)

From  About.com I think I found something that ilustrate pretty well the use of "Il Faut" (Sorry to refer you to web pages, my english is not quite good enough to explain it right)

Falloir is an irregular impersonal French verb that is better known in its conjugated form: il faut. Falloir means "to be necessary" or "to need." It is impersonal, meaning that it has only one grammatical person: the third person singular. It may be followed by the subjunctive, an infinitive, or a noun:

   Il faut partir
   It's necessary to leave

   Il faut que nous partions
   We have to leave

   Il faut de l'argent pour faire ça
   It's necessary to have money to do that / You need money to do that

When falloir is followed by an infinitive or noun, it may be used with an indirect object pronoun to indicate who or what needs whatever comes next:

   Il faut manger
   It's necessary to eat

   Il nous faut manger
   We have to eat

   Il faut une voiture
   It's necessary to have a car

   Il me faut une voiture
   I need a car


Expressions with Falloir

Falloir is used in a number of expressions, including:

   ce qu'il faut - what is needed

   Il a bien fallu ! - I/We/They had to!

   s'il le faut - if (it's) necessary

   Faudrait voir à voir (informal) - Come on! Come off it!

   Il faut ce qu'il faut (informal) - You've got to do things right

 

Hope it Help

Yanick