This is the 5472nd most frequent French word.
bill
"Bill" in French means "note" (a piece of paper money) or "bill/invoice" (a statement of charges).
Here, 'billet' means 'ticket', which is another usage of the word 'bill' in the context of tickets or entry passes.
Elle a perdu son billet de train et a dû en acheter un nouveau.
She lost her train ticket and had to buy a new one.
In this case, 'billet' refers to a paper currency note, commonly used for making payments.
Il a donné un billet de vingt euros pour payer le dîner.
He gave a twenty-euro bill to pay for dinner.
In this sentence, 'facture' refers to a bill as an invoice for services or utilities.