ASD is a developmental disorder that is characterized by repetitive behaviors and poor social skills.

Autism is not usually noticed until the child diagnosed with has trouble interacting with others around their age.

The thinking of autism has changed over time. In the past children were diagnosed with different conditions known as pervasive developmental disorders:
- autism
- Asperger's disorder
- childhood disintegrative disorder (CDD)
- pervasive developmental disorder not otherwise specified (PDD-NOS)

All of the above conditions are now considered different forms of autism. Autism comes with a range of symptoms and behaviors, so autism is now considered a spectrum of disorders.