Hierarchical Classification is a system of grouping things according to a hierarchy, or levels and orders. A hierarchy can be seen in positions of authority in which people are ranked in an unwavering order of authority, with a "boss" at the top and "entry level" employees at the bottom. The military uses hierarchical classification to organize its members: generals are at the very top, followed by colonels, captains, and then sergeants.
The categorization of species is another example of hierarchical classification. At the very top is the kingdom which is the broadest category, followed by phylum, class, order, family, genus, and species. For humans, the classification would be Animalia (kingdom), chordata (phylum), class (mammalia), order (primates), family (hominidae), genus (homo) and species (sapien). It goes from a very broad category (all animals) all the way down to our unique species (sapiens).