How might a 4 year old with autism be different to a 4 year old without?

I am just interested in how they would be different. I know it varies from child to child but I would just like to know how they might differ. I may be nanny-ing for a 4 year old boy with autism and would like to know how he may be different from a 4 year old without autism. Any help you can give me would be appreciated before I actually meet this boy.