Taxonomy is the branch of biology dealing with the identification, nomenclature and classification of organisms based on their characteristics. A taxon is a unit or group of organisms of any rank in classification (for example, mammals, insects, dogs). Taxonomic hierarchy is the arrangement of taxonomic categories in a definite descending order, from kingdom down to species.

Binomial nomenclature is the system of naming organisms with two words, given by Carolus Linnaeus, where the first word is the genus and the second is the species (for example, Mangifera indica for mango). Rules: (1) the generic name begins with a capital letter and the specific name with a small letter; (2) the biological name is printed in italics (or underlined separately when handwritten) and is usually in Latin.

The taxonomic categories in descending order are: Kingdom, Phylum (Division in plants), Class, Order, Family, Genus and Species. Species is the lowest category and represents a group of individual organisms with fundamental similarities that can interbreed. As we move up the hierarchy, the number of common characteristics decreases while the number of organisms in the group increases.