Cuban currencies

There are two official currencies in Cuba - Cuban Pesos (CUP) and Cuban Convertible Pesos (CUC).
CUP is local currency - Pesos and Moneda Nacional (National money). There is a limited range of goods that can be bought for local pesos – vegetables, fruits, local cigars (tabacos) fresh juices and snacks from street vendors.
CUC is the currency made for tourists in Cuba. CUC is used to pay for hotels, official taxis, meals at restaurants, entry into museums, cigars, rum and other visitors needs. Conversion into CUC can be done at exchange offices (casa de cambio, or cadeca). Exchange offices are located in hotels and in other tourist hubs throughout the cities. CUC are valued at 25 times the value of CUP.
Because the products that can be purchased with CUP are limited, it is not a good idea for tourists to change a lot of CUC into CUP. It is recommended to have some CUPs, because some goods from street vendors costs 5 times less than 1 CUC, so the only way to pay the real price is to have some CUPs.

(This text is taken from www.topholidaydestination.info)