C’è (from ci è) and ci sono correspond to the English there is and there are. They state the existence or presence of something or someone.
C’è tempo; non c’è fretta. (There's time; there is no hurry.)
Ci sono molti italiani a New York. (There are many Italians in New York.)
C’è and ci sono should not be confused with ecco (here is, here are; there is, there are), which is used when you point at or draw attention to something or someone (singular or plural).
C’è una parola difficile in questa frase. (There's a difficult word in this sentence.)
C’è and ci sono also express the idea of being in or being here/there.
Scusi, c’è Maria?— No, non c’è. (Excuse me, is Maria in?— No, she isn’t.)
Come is used with all persons of essere in questions to find out what people or things are like.
Come sei? (What are you like?)
Com’è il museo d’arte moderna? (What is the museum of modern art like?)
Come + essere is used in exclamations.
Come sei biondo! (How blond you are!)
Com’è dolce questo caffè! (How sweet this coffee is!)
Come sono buoni questi panini! (How good these sandwiches are!)
Note the word order: come + verb + adjective. The subject, if expressed, is at the end of the exclamation.
Com’è grande questo museo! (How big this museum is!)
Exclamations of this kind are used much more frequently in Italian than in English.
Com’è bella questa casa! (This is really a nice house! My, what a lovely house!)