Binomial nomenclature means the system of classifying something, such as an animal or plant, with two names; the first name referring to the genus (branch of family) to which it belongs and the second identifying its species, or specific group.
The binomial nomenclature for lion is Panthera leo. Panthera means great cat, showing that lions belong to the same genus as the leopard, the panther and the tiger. The word leo is Latin and comes from the Greek leon; this was the name given to the lion by ancient Greek naturalists. The lion or Panthera leo evolved in Africa about a million years ago.
The family to which the genus Panthera belongs is the Felidae, or cats. The other genus in this family is the Felinae, to which the domestic cat belongs as well as smaller cats like the lynx, cougar etc. Hope this helps.