A species is said to have an asexual reproduction when it can reproduce without the intervention of a congener of the opposite sex. All the formed individuals correspond to clones: their genetic inheritance is identical to that of the mother.
Vegetative propagation can be observed in animals, plants and bacteria.
"Anterior" means "to the front". A horse's head is anterior to the rest of its body. Contrariwise, "posterior" means "to the back", like a horse's tail. Hope that helped! =)