What does 'Australopithecus boisei' and 'Australopithecus robustus' mean?

Australopithecus boisei and Australopithecus robustus are two different species of Australopithecines that lived around the same time. A. boisei lived 1.4 to 2.25 million years ago while A. robustus lived 1.5 to 2 m.y.a. It is believed by most paleoanthropologists that their genetic lines died out and they did not leave any evolutionary descendants.