Parasites are organisms that live on or inside another host organism, taking nutrients and resources from it. They can be found in various forms, such as worms, protozoa, and insects. While some parasites cause diseases in their hosts, others may not have noticeable effects. Common examples include tapeworms in the intestines and lice on the scalp. These organisms have evolved to survive by relying on their hosts for food and shelter. In some cases, parasites can significantly impact the health of their hosts, leading to symptoms like fatigue or illness. Understanding parasites is essential for preventing and treating infections in both humans and animals.