Travelling to Cuba brings you the strange situation that within the country two currencies are circulating: CUP and CUC. The Cuban peso (CUP) is the actual currency of Cuba, divided into 100 Centavos. As it is a weak currency, the US dollar was used in addition on the island.
Using the money of the archenemy was a problem in the eyes of the Cuban government and therefore the peso cubano convertible (CUC) was introduced, its value tied to that of the US dollar. Wages are paid in CUP, but there are a lot of goods that a local can only buy with CUC. That is why people like jobs in the tourism industry because the can get tip in CUC.
As a tourist you can get only CUC and pay almost everything with it. But you can also exchange CUC against CUP on the streets. Be careful: often signs don’t tell you wether a price is denoted in CUC or CUP. A nice trick to get CUC is to offer the 5 CUP coin – showing Ernesto “Che” Guevara – for 5 CUC. A bad deal, but if it happens to you, consider it as a donation.