Binomial nomenclature is when a two word system for naming different species. The first word is genus, and the second is species. The reason for this two part name is so it is universal and understood by people across the world.
Is a dolphin a fish or a mammal? That is a question that people in Linnaeus’s time had problems with. Although dolphins live in water and have fins like fish, they are warm blooded and breath air like mammals.
There are six categories of life called kingdoms. They are Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia. There are three bigger categories called domains. They are Bacteria, Archaea, and Eukara.