People usually call it autism (say: aw-tih-zum), but the official name is autism spectrum disorders. Why? Because doctors include autism in a group of problems that kids can have, including Asperger syndrome and others. These problems happen when the braindevelops differently and has trouble with an important job: making sense of the world.
Every day, our brains interpret (understand) the things we see, smell, hear, taste, touch, and experience. But when someone's brain has trouble interpreting these things, it can make it hard to talk, listen, understand, play, and learn.
A kid's symptoms could be very mild, severe, or somewhere in the middle. For example, some kids might be upset by too many noises or sounds that are too loud. Kids who have milder symptoms don't mind loud noises so much. Someone with mild symptoms might need only a little bit of help. But a kid with severe symptoms might need a lot of help with learning and doing everyday stuff.
Kids with autism often can't make connections that other kids make easily. For example, when people smile, you know they feel happy or friendly; when people look mad, you can tell by their face or their voice. But many kids who have autism spectrum disorders have trouble understanding what emotions look like and what another person is thinking. They might act in a way that seems unusual, and it can be hard to understand why they're doing it.