The ICZN only applies to animal names, and not to names of plants, fungi, bacteria or viruses, which are covered by separate codes of nomenclature.
Animals include metazoans and protists that have been historically considered in the Kingdom Animalia (i.e., protists that do not primarily use photosynthesis as an energy source, if so they are generally considered to be plants and will fall under the botanical Code, ICBN). Although higher-level classifications have changed with modern research, which Code (Zoological, Botanical or Bacterial) covers a particular taxon generally remains constant, as it is agreed that the ultimate goal of nomenclatural rules is to maintain stability in names and not to reflect perspectives on phylogenetic relationships. Thus, for example, fungi remain covered by the Botanical Code, and there is little interest in changing this, despite modern consensus that they have a sister relationship with animals and not plants. Protists that have characteristics of both animals and plants are considered ‘ambiregnal’ and are treated following the rules of both the ICZN and ICBN.
Fossil animal taxa and animal trace fossils, or ichnotaxa, are covered by the ICZN. Domesticated animals (defined as distinguished from wild progenitors by characters resulting from selective actions of humans) are also covered by the ICZN. Scientific names for collective groups of animals are also covered (though without anchoring on a type specimen), such as the name Cercaria O.F. Muller, 1773 for trematode larvae that cannot be placed with confidence in known genera.
The ICZN does not cover names for hypothetical concepts (e.g. the Hypothetical Ancestral Mollusc or the Loch Ness Monster), teratological specimens (monstrosities), or hybrid specimens (although taxa of hybrid origin are covered).