>>69853556it's the leaves of a holly plant from south america, dried and roasted for use as a drink (high in caffeine). you stuff it into a cup, pour in hot water, and then drink it through a filtered straw rather than filtering out the leaves. "yerba mate" basically means "gourd herb" because they'll make a big container of it and share it around. it was turned into a big commodity by missionaries building communes/monasteries and teaching the natives to grow it commercially (instead of just a couple of tribes foraging it).