The main distinctions in the African rhinoceroses lays not in their horn number or colors, but in their diet. The black rhinos have a prehensile upper lip, and are able to use it to strip the leaves off of trees and bushes (browsers), while the white rhinos (from Afrikaans, wyd/wijd = wide, referring to the wide mouth) are much more adept at being pure grazers, cutting the grass with their squared-off mouth.
The two African rhinos both have two horns. The Indian rhino only has one horn, as does the Javan Rhino. The Sumatran rhino has two horns, though in females they’re often just knobs or not there at all.
Zoology. Published by Frederick Warne, mid-1800s.