The father of taxonomy, Aristotle, was the first to develop a classification system for living organisms. His system was very simple and did not go into much detail of organisms. Using Aristotle's method, first you looked at the blood. If the blood was red it was an animal, and if the blood was not red it was a plant. To farther classify animals, he divided them by how they traveled; if they fly, walk on land, or swim.
Carolus Linnaeus made the second classification system. He also separated organisms into two kingdoms; plants and animals. The next of his steps was to divide the organisms into groups called genera, then by species. He also made a way to name organisms called binomial (two names) nomenclature (system of naming). Every organisms has two names, genus and species name. The genus name must be capitalized, but never the species name. Also the whole name needs to be either underlined or written in italics.
Today's classification system is based off of Linnaeus's. Today we have six kingdoms instead of Linnaeus's two. The six kingdoms are plants, animals, fungi, protists, archaebacteria, and bacteria. After separating between these you can separate organisms by there phylum, or the makeup of the body; humans belong to the chordata phylum. Next you find out the organisms class, for example; fish, mammal, or bird. To further classify an organisms, you need to find its order; this could be separating mammals that are carnivores or herbivores. The family is the next classification; for example carnivores can be felidae (cats, cheetahs). Genus comes after family; felidae can be Panthera which give them the ability to roar. Then comes species, which is the smallest classification of an organisms; in the Panthera genus, one organisms species is Tigris. Using this the binomial nomenclature of this organism is Panthera Tigris.