0 used to ask for information about something -- o que
What time is it?
What’s this?
1 used when you have not heard what someone has said and you want them to repeat it -- quê?, como?
2 used to mean something without giving it a name -- que, o qual, a qual
3 used to ask what someone wants when they call you -- o quê?
‘Jenny?’ ‘Yes, what?’
4 used to suggest something -- e se…?, que tal…?