The video "What Are Platyhelminthes?" introduces viewers to the fascinating world of flatworms, also known as platyhelminthes. Characterized by their soft, invertebrate bodies and vast diversity, with over 20,000 species, these organisms play significant ecological roles. Key topics include the concept of parasitism, as 80% of flatworms rely on host organisms, the process of diffusion for oxygen absorption, and the evolutionary development of the mesoderm, which facilitates organ and muscle formation. Without a complete digestive system, flatworms have unique excretory systems involving flame cells. The video also explores the different types of flatworms, such as parasitic tapeworms and flukes, along with planarians, which are commonly studied in biology classes for their regenerative abilities. This educational content aligns with science curricula, emphasizing invertebrate biology and parasitology.