Cestodes, commonly known as tapeworms, are a type of parasitic flatworm that live in the intestines of various animals, including humans. They have a long, ribbon-like body made up of segments called proglottids. These segments can grow to be quite long, allowing the tapeworm to absorb nutrients from the host's food. Tapeworms are typically transmitted through contaminated food or water, often from undercooked meat or fish. Once inside the host, they can cause digestive issues and other health problems. Proper hygiene and cooking practices are essential to prevent cestode infections and maintain good health.