Autism is usually used to describe a difficulty in understanding social situations. People who have autism may have difficulty understanding what is appropriate in conversation, interpersonal relations, or interacting with large groups of people by displaying “strange” behaviors.
These can include talking for great lengths of time about certain subjects past the group’s interest, or being unable to pick up on social cues (being uninterested in a certain topic of conversation, subtle clues towards guiding the direction of a conversation, etc.).
Autistic people process information on people with the ‘objects’ part of the brain, instead of the ‘social’ part. Thus, social norms and effects of ones behaviour on others are not considered, relevant or even understood.
Ever been somewhere completely foreign? The people talk strange, dress strange and act strange. Toilets flush the wrong direction, cars on the wrong side of the road. People on the street will stand too close to you or get angry if you point with one finger.
All kinds of shit that leaves you with a vaguely uncomfortable feeling. You can communicate with people, although misinterpretations are common, and you can interact enough to get by, but you can never really get your point across when needed, and you just plain don’t have a grap of their social norms. Pretend this never gets better. That’s kind of how we think an autistic feels.
It depends, of course, on where one lands on the aforementioned “autistic spectrum”, but holds true to some extent with all autistics.
It’s hard to get your point across or to get someone else’s point, others emotions or reactions to events make no sense, and are unpredictable to an autistic.
It is honestly surprising to a person with autism that the neighbor would get mad at you for smashing his car windows with a hammer. You’d be confused if he liked his windows, or just hates that hammer.
A lot of folks with autism cling to things like math for comfort. They like patterns, predictable things that always have a familiar outcome.
Check out The Curious Incident of the Dog in the Night-Time . Amazing story told from the point of view of an autistic child.