For centuries, the naming and classification of living organisms into groups has been an integral part of the study of nature.
Aristotle (384BC-322BC) developed the first known method of classifying organisms, grouping organisms by their means of transport (air, land, water). A number of other naturalists followed with other classification systems, but it was Swedish botanist, Carolus Linnaeus (1707-1778) that is considered to be the pioneer of modern taxonomy.
In his book Systema Naturae, first published in 1735, Carolus Linnaeus introduced a rather clever way to classify and name organisms. This system, now referred to as Linnaean taxonomy, has been used to varying extents, ever since.
About Linnaean Taxonomy
Linnaean taxonomy categorizes organisms into a hierarchy of kingdoms, classes, orders, families, genera, and species based on shared physical characteristics. The category of phylum was added to the classification scheme later, as a hierarchical level just beneath kingdom.
Groups at the top of the hierarchy (kingdom, phylum, class) are more broad in definition and contain a greater number of organisms than the more specific groups that are lower in the hierarchy (families, genera, species).
By assigning each group of organisms to a kingdom, phylum, class, family, genus, and species, they can then be uniquely characterized. Their membership in a group tells us about the traits they share with other members of the group, or the traits that make them unique when compared to organisms in groups to which they do not belong.
Many scientists still use the classification system today, but it is no longer the only method for grouping and characterizing organisms. Scientists now have many different ways of identifying organisms and describing how they relate to each other.