In a literal sense, voilà means something like There it is. Voilà le monsieur qui parle anglais. There's the man who speaks English.
On the other hand, voilà is sometimes used as an exclamation, perhaps like "Bingo," in English.
Eh voilà, c'est une longue histoire (from Un homme et une femme).
How is voilà used informally, and does it have any particular meaning in this regard?