• c’è and ci sono are also used to find out if someone is in:

C’è Giovanni? Is Giovanni in? Is Giovanni there?   No, non c’è No, he isn’t in.

Ci sono Maria e Giulio? Are Maria and Giulio in?    No, non ci sono No, they’re not in.

• c’è is also used to enquire what’s wrong:

Che c’è? What's up? What's wrong?

• c’è...? is made up of ci, there, and è, is. It is awkward to say ci è, so ci becomes c’ in front of è and is pronounced as one word.
• ci changes to ce when it's used with ne. This word has no exact equivalent but roughly corresponds to '...of it' or '...of them':

C’è un cinema in centro? Is there a cinema in the centre?

Sì, ce ne sono Yes, there are some (of them).    No, non ce ne sono No there aren’t any (of them).

Sì ce ne sono tre Yes, there are three (of them).