Taxonomy may refer to either a hierarchical classification of things, or the principles underlying the classification. Almost anything -- animate objects, inanimate objects, places, and events -- may be classified according to some taxonomic scheme.
Mathematically, a taxonomy is a tree structure of classifications for a given set of objects. At the top of this structure is a single classification - the root node - that applies to all objects. Nodes below this root are more specific classifications that apply to subsets of the total set of classified objects. So for instance in Carolus Linnaeus's Scientific classification of organisms, the root is the Organism (as this applies to all living things, it is implied rather than stated explicitly). Below this are the Kingdom, Phylum, Class, Order, Family, Genus, and Species, with various other ranks sometimes inserted.
Anthropologists have observed that taxonomies are generally embedded in local cultural and social systems, and serve various social functions. Perhaps the most well-known and influential study of folk taxonomies is Emile Durkheim's The Elementary Forms of Religious Life. The theories of Kant and Durkheim also influenced Claude Levi-Strauss, the founder of anthropological structuralism. Levi-Strauss wrote two important books on taxonomies; Totemism and The Savage Mind.
Such taxonomies as those analyzed by Durkheim and Levi-Strauss are sometimes called folk taxonomies to distinguish them from scientific taxonomies that claim to be disembedded from social relations and thus objective and universal. The most well-known and widely used scientific taxonomy is Linnaean taxonomy which classifies living things and originated with Carolus Linnaeus. This taxonomic system is accessible from the article evolutionary tree.