Fungi are a kingdom of eukaryotic (their cells have nuclei) organisms. Other examples of biological kingdoms include Plantae, the plants, and Animalia, the animals.Common fungi include mushrooms, yeasts, and molds.lthough fungi may look like plants, they are in fact more closely related to animals. The study of mushrooms is known as mycology. The key characteristic of fungi which sets them apart from other organisms are their chitinous cell walls.