The other day I was at a bar in Peru and overheard the following conversation:

Guy: Two Cuba Libres, please.

Bartender: Uh, two rum and cokes?

Guy: No, two Cuba Libres.

Bartender: (to other, better bartender) What’s a Cubra Libro?

Guy: Oh, fuckin’ hell (with English accent).

Just so you know, the difference is lime juice.  Although, to be fair, in Peru they squeeze fresh lime juice in no matter what you call it, so there is no fucking difference.

………and knowing is half the battle.