C’est is neutral and used for general statements. il/Elle est is used when you refer to a specific noun you already mentioned, and it takes the gender of that noun. If you are making a general comment, use c’est. If you are talking about a thing directly and replacing the noun, use il/elle with the right gender.

It's because in French, every noun is either masculine or feminine. So if you spoke about your car, the car is a feminine noun. Instead of saying "the car" again, you would say "it" instead and we need to use the feminine form of "it". That is why when some French speakers are learning English they may say things like 'The car looks nice but she doesn't work.' English doesn't have a masculine or feminine form of "it" but French does. If you decide to learn Spanish, Italian, or Portuguese you will deal with this same concept in those languages as well. I hope this helps.