There is only one monetary unit for the world of Vegas. It is commonly called a credit or cred but also goes by any number of slang terms. Units, bucks, dollars, quid, k's, plus many other terms are used.
Money exists electronically only. Money is carried on cards. C-card, D-card, I-cards, business cards. There is no physical money.
Money on C-cards most resembles the cash of the old world. Money can be transferred from card to card. Many people keep several c-cards on hand with different amounts on them so that whole cards can be passed.
I-cards attach the name of the owner to the cash so that it can be traced. I-cards are also used to access the owner's bank account.
Credit can also be put on D-cards and business cards but isn't commonly done.