A flea is a small, wingless insect that belongs to the order Siphonaptera. These parasites are known for their ability to jump long distances relative to their size, which helps them move between hosts. Fleas feed on the blood of mammals and birds, making them common pests for pets like dogs and cats. Fleas have a flat body that allows them to navigate through the fur of their hosts easily. They reproduce quickly, with females laying hundreds of eggs, which can lead to infestations. Flea bites can cause itching and irritation in both animals and humans, and they can also transmit diseases.