Peaberry is a natural mutation of the coffee bean inside its cherry. Peaberries are rounder, smaller single berries inside of a coffee cherry instead of the normal two halves. It is like a single child instead of twins, but in the coffee world twins are the norm and a single peaberry is an anomaly.
The different structure results in sweeter and more flavorful coffee compared to regular beans from the same area.
Approximately 5% of coffee comes in peaberry form.