What the heck is a Guava?

Not sure even how to say it...

Benefits:
source of Vitamin C
soluable dietary fibre

potassium and iron

Draw backs:
expensive and rare
sulfites in dried guavas may provoke an asthma attack or allergic reaction

Only 60 calories per fresh guava makes a interesting, nonfattening dessert. Simply cut in half and scoop out the seeds, then scoop out the flesh. A dash of lime juice or lemon juice contrasts nicely with the sweet flavor.

There are so many things in the grocery store that I have never used, Do you have any ideas or recipes for some rare ingredients