According to a Rice University webpage, the five-kingdom system is a method of classifying life forms into five separate categories. The system is an expansion of the previous two-kingdom model of plants and animals.
The five kingdoms are as follows: Protista consists of single-celled eukaryotes, Fungi consists of fungus and other similar organisms, Plantae includes all plants, Animalia includes all animals and Monera consists of the prokaryotes. A significant number of biologists divide Monera into two kingdoms of Eubacteria and Archeobacteria, extending the number of recognized kingdoms to six. Members of the Protista and Monera kingdoms are single celled, while members of the remaining three kingdoms are multicellular.