Animals such as dogs and cats have been domesticated by people. This means that people have raised and cared for these animals for thousands of years, until many of the animals' wild instincts faded. If you watch a kitten pounce on a toy, or know that your dog thinks of you as his "pack", you will understand that pets still have some of their instincts left - even after all these years! However, their instincts aren't strong enough for them to live safely in the wild anymore. They need people to care for them, and they often get along well with human beings.
Wild animals have strong instincts, even when they are born in captivity. It takes thousands of years of breeding to turn a wild animal into a domestic pet. Some people try to keep wild animals as pets, and we call these "exotic pets". Many people think that it is ok to keep these animals as pets because they are often sold in pet stores. But just because an animal is sold in a pet store doesn't mean that it's a good pet!
