PDD-NOS is one kind of autism spectrum disorder (ASD). ASD is the umbrella designation for what are now considered a variety of disorders (Asperger's syndrome, autism, and PDD-NOS).

The designation "high-functioning autism" doesn't have any real diagnostic validity. "High functioning" means that IQ is unimpaired; but it has nothing to do with the severity of the autism. A person can have a high IQ and really significant impairments from autism.

HTH,
DeeDee