Article / Updated 03-26-2016
Some people classify autism spectrum disorders into subtypes by their presumed causes, but because science hasn't yet resolved the causes, this practice is controversial and not widely accepted. But you can look at autism as a spectrum ranging from severe to light.
People with severe autism might be greatly disabled, whereas those with high-functioning autism (HFA) and Asperger Syndrome may be affected so slightly that their autism doesn't play a major role in their lives.