What is what is in French?

Great question. French has difficulty with this sort of question. The most elegant answer is qu'est-ce que, as in Qu'est-ce que l'amour? - What is love? BUT nine out of ten French people will go further and use Qu'est-ce que c'est que: Qu'est-ce que c'est que l'amour? In conversational slang, C'est quoi? (what is it?) is common: C'est quoi, l'amour? This is also the simplest construction.