What is Autism? Bing's Dictionary gives a good short overview-
"condition disturbing perceptions and relationships: a disturbance in psychological development in which use of language, reaction to stimuli, interpretation of the world, and the formation of relationships are not fully established and follow unusual patterns"
What does that actually mean? People with Autism often don't precieve things well in social situations. They may not be able to read facial expressions, body language, or may not use eye contact. Many people with Autisum don't understand sarcasm. They often have sensory issues, such as not liking the feel of clothes most people find comfortable or finding sounds to loud that most other people can easily tolerate. People with autisum may become fustrated and throw tantrums.
There are different types of Autism and different levels of functioning. Some people with autism never speak while others can go on to regular colleges with little help. Asperger's Syndrome is mild form of autisum. Autisum may also be refered to as ASD (Autism Spectrum Disorder).
Feel free to ask questions.