"What Are Nematodes?" is an educational video exploring the fascinating world of nematodes, which are among the most diverse animal species on Earth. Covering up to 500,000 types, the video explains how these tiny worms, such as roundworms and hookworms, range from microscopic to three feet in length, with most being around two inches. They exhibit unique anatomical features like radial symmetry in the head and bilateral symmetry in the body. Key topics include nematodes' anatomy and feeding mechanisms, highlighting their stylet, a specialized organ for injecting enzymes or sucking liquids. The video discusses the parasitic nature of 15,000 documented nematodes and their impact on health, like heartworm in pets, while also emphasizing beneficial nematodes that control garden pests. Offering insight into nematodes' ecological role and scientific research for managing harmful species, the video is vital for understanding the biological intricacies contributing to environmental balance.