Recently i saw the phrase, "c'est un bon homme" which really confused me because, why isn't it "il est un bon homme?" I think this mostly confused me because i always thought you would use il est when describing or talking someone? For example you would say "il est un homme" not " c'est un homme" right? Can someone please explain?
When describing people and things with être in French, you usually can't use a personal subject pronoun like il. Instead, you must use the impersonal pronoun ce, which can also mean "this" or "that". Note that ce is invariable, so it can never be ces sont.
These pronouns aren't interchangeable. The basic rule is that you must use ce when être is followed by any determiner - for instance, an article or a possessive adjective. Note that c'est should be used for singulars and ce sont should be used for plurals.
C'est un homme. - He's a man. / This is a man. / That is a man.
If an adjective, adverb, or both appear être, then use the personal pronoun.
Elle est belle. - She is beautiful. (Or "It is very beautiful")
As you know, nouns generally need determiners, but one important exception is that professions, nationalities, and religions can act as adjectives after être. This is optional; you can also choose to treat them as nouns.
He is a doctor. - Il est médecin. / C'est un médecin.
However c'est should be used when using an adjective to make a general comment about (but not describe) a thing or situation. In this case, use the masculine singular form of the adjective.
C'est normal ? - Is this normal?
"c'est un bon homme" sounds odd to me, mainly because it sounds like "c'est un bonhomme" which as a slightly different meaning. Seems like common translations are "old fellow", "chap", but the meaning is rather context-sensitive (it can be laudative or mocking depending on how it's used). For instance "bonhomme de neige" means snowman. For this reason if I wanted to say "he's a good man" I'd say "c'est un homme bon" even though usually the adjective "bon" precedes the object.
Now on the subject of "c'est" vs. "il est/elle est" you would never use the latter to say "he's a man", I think mainly because we see it as redundant. And you'd definitely say "c'est un homme", never "il est un homme".
Like Lyra Keiken said you can use both "il/elle est" and "c'est" for nationalities and vocations, so "il est russe", "c'est un russe" for instance. Note the lack of "un" with the "il est" form.
Applying the same rule I guess you could technically say "il est homme", "elle est femme" but that sounds very literary/poetic to me, not something you'd say factually in a conversation. Sounds like you're saying "his/her very essence is being a man/woman". Definitely not something you'd say often.
It's a bit weird to me too . If you want to say that someone is a good man , as liofla sais "c'est un homme bon " or even more used "c'est quelqu'un de bien" ...but the meaning is a bit different and it can be used for a man or a woman .
What is the context of the sentence you've found ? Where did you see it ?