"What is it?"
I just added it as a possibility. They do have different meanings, however, and are used in different contexts. "Cosa c'è?" (And "Che c'è?") means "What is it?" as in "What's wrong?" "Cos'è?" (and also "Che cos'è" and "Che è") means "What is it?" as in "What is this thing?"
Thanks for your answer. I don't edit my post because if i do yours become difficult to understand. And it is really interesting. You did great for the spread of Italian through the world. Alone, at the beginning, if I remember well. Volevo dirtelo da molto tempo: Bravo Fernando!
If you're not sure, I would start by guessing the accent points down (è grave accent) as that's the majority. There are only a few words where the accent points up (é acute accent). Perché is one of the few words with an acute accent, so that's worth remembering.
Note the accent tells you which way your voice should go, i.e. an accent point up, your voice goes up, and then down for down. Note there's no rule for which words have acute or grave accents, so you just have to learn them.