What IS autism? Per the American Psychiatric Association, Autism Spectrum Disorder "is a complex developmental condition involving persistent challenges with social communication, restricted interests, and repetitive behavior." The key word here is "complex." Because everyone with autism is a unique individual who manifests a different combination of symptoms, each to different degrees. In fact, many people and organizations are now using a wheel diagram to describe an individual's symptoms rather the linear lower- to higher-function model.
Resources for More Information
National Autism Association
Autism Parenting Magazine
American Academy of Child & Adolescent Psychiatry, Autism Resources
National Autism Resources
Autistic Self Advocacy Network