It differs from area to area and doctor to doctor.
Here, they use the term ASD to mean anyone with any dx on the autistic spectrum, no matter if it's low-functioning or high functioning. Even, sometimes, for Aspergers, though they usually dx that separately with the specfic name, followed by the words 'a mild and subtle form of autism'...which is so not what Aspergers officially is, but hey!
It gets more complicated, because on the ADOS test (a play based assessment commonly used to assess), they use the term ASD to mean mild and the term autism to mean severe.
So my J scored in the autistic range (nearly 100%) on the ADOS test and the official dx came through as ASD...psych said, that's what we say for everyone unless iit's Aspergers. Why didn't he have Aspergers, I asked. She said, because it's too severe.
This is not what the diagnostic criteria says!
So, here's my summary, but your area might not follow the 'rules' - mine doesn't!
ASD is the umbrella term for anything on the spectrum.
Autism (LFA or HFA) is a person who meets the criteria for the triad of impairments.
A dx of autism usually means that there must have been a language impairment before the age of 3.
A dx of Aspergers usually means that there was no problem with language, but problems can still be severe.
I hope I've got this right.
So ASD and autism are used pretty much interchangably here - people tend to understand the latter one better though.
3.5 min consultation I hope that's a typo?