Coffee comes from the latin form of the genus Coffea, a member of the Rubiaceae family which includes more than 500 genera and 6,000 species of tropical trees and shrubs.
After three to four years, when they reach maturity, coffee trees bear fruit in lines or clusters along the branches of the trees. Referred to as a berry or cherry, this fruit turns red when it is ready to be harvested.
Coffee beans are actually the seeds of these ripened cherries. Most arabica cherries ripen after 6-8 months; robusta beans take between 9 and 11 months to ripen.
Beneath the cherries' red skin is a fleshy pulp, a slimy layer, and a parchment like covering of the bean. Inside these layers are usually two beans, which are covered by a thin membrane or coat. This membrane or seed skin, is referred to in the coffee trade as the "silver skin".