The Kingdom Protista includes single-celled eukaryotic organisms known as protists. Protists obtain energy through photosynthesis or consumption of organic matter, and can be found in various habitats around the world. They reproduce through mitosis or meiosis and cell division. Protists are classified based on characteristics like cell structure, energy source, and habitat. Examples of protists include algae, protozoa, water molds, and slime molds.