Guava is a fruit with many names and many types, generally belonging to the genus Psidium. In Costa Rica, cas is a guava that is used to make delicious juice and has yellow or whitish, seed-filled flesh. In Nicaragua, cas is known as guayaba. And to an American English speaker, guava (the red-fleshed fruit often used to make guava jelly) is what ticos call guayaba, whereas ‘guava’ refers to a bean-like fruit from a tree in the genus Igna… I think. I’ve also heard cas referred to as ‘superfruit’ in English.
In any case, all of the fruits are good… unless they are parasitized by fly maggots. Or perhaps, that’s what you’re into: