Autism is a developmental condition that causes atypical behaviour.
The condition's severity varies, for some it barely makes a difference and for others it is impossible to live without assistance.
It is genetic and is not caused by vaccines or any other external factors.
Asperger's syndrome was a term used to describe people with high-functioning Autism, but it was merged with the more broad diagnosis of Autism Spectrum Disorder due to it being a subset of it.
While the term is still used in conversation today, it is very controversial due to the person who it was named after being a Nazi scientist.