The Autism Society of America has published a good overview of Autism Disorder and Asperger's Syndrome on TylerPaper.com . The article contains a basic description of both Autism Disorder and Asperger's Syndrome and helps distinguish between the two similar but distinct disorders:
What distinguishes Asperger's Syndrome from autism is the severity of the symptoms and the absence of language delays. To the untrained observer, a child with Asperger's may seem just like a normal child behaving differently. They may be socially awkward, not understanding of conventional social rules, or show a lack of empathy. They may make limited eye contact, seem to be unengaged in a conversation, and not understand the use of gestures.
One of the major differences between Asperger's Syndrome and autism is that, by definition, there is no speech delay in Asperger's. In fact, children with Asperger's frequently have good language skills; they simply use language in different ways. Speech patterns may be unusual, lack inflection, or have a rhythmic nature or it may be formal, but too loud or high pitched. Children with Asperger's may not understand the subtleties of language, such as irony and humor, or they may not recognize the give-and-take nature of a conversation.
Another distinction between Asperger's Syndrome and autism concerns cognitive ability. While some individuals with autism experience mental retardation, by definition a person with Asperger's cannot possess a "clinically significant" cognitive delay, and most possess average to above-average intelligence.