This website Autism Understood may be helpful, it is specifically designed by autistic people for younger members of our community to understand their autistic neurology and identity.
Hi NAS93502, you may find it useful to have a look at the autism page on our website which has a vast amount of information which could be useful for your son. The page contains information on the basics of what the autism spectrum is, how it's defined in a clinical sense, and the characteristics of autism:
