In many places, Cats can go outside and be beneficial to the community. Cats benefit from going outside, usually cats going outside are happier and less obese than cats inside.  Cats can face separation anxiety and depression when they are kept indoors all the time. Remember, your cat is still an animal. If they are desperate enough, cats will try to escape frequently. Cats love running around in the grass and exploring your neighborhood.  Before you let your cat outside, make sure you are bonded with your cat and trained to come when called. Another benefit from letting your cat outside is that if you have a neighborhood with a lot of mice, chipmunks and groundhogs, a cat's presence can help control the population of these creatures.  Cats will also keep away opossums, squirrels and raccoons. 

Cats are responsible for killing a lot of song birds and native animals in a region. Letting your cat outside can lead  to more bad things, including your cat getting hurt, fighting with other cats and animals or getting hit by a car. If you live in a very busy area, you should NEVER let your cat outside. There is also a chance that your cat can get kitty AIDS from a fight with another cat. Another reason is because if you don't use good flea and tick treatment, it is very likely you can get an infestation.  There are a lot of animals that can stand up to a cat, dogs, raccoons, opossums. Sometimes a cat will be tough enough to withstand the threat. But some cats are definitely not fighters and can get fatally injured by these animals.