Platyhelminthes, commonly known as flatworms, are a diverse group of invertebrates characterized by their flattened bodies. They can be found in various environments, including freshwater, marine, and terrestrial habitats. This phylum includes notable classes such as Turbellaria, Trematoda, and Cestoda, which encompass free-living and parasitic species. These organisms exhibit a simple body structure without a coelom and possess bilateral symmetry. Some flatworms, like Planaria, are known for their remarkable regenerative abilities, while others, such as tapeworms, are significant parasites in many animals, including humans. Their unique biology makes them a fascinating subject of study in evolutionary and ecological research.