PDD-NOS is a diagnosis, as others have said, that is given when a child meets some of the critera for being on the autism spectrum, and it is viewed as being "higher functioning". Even so, your child will still qualify for therapy and help from either the state or the school district or both. Even though your child may have been diagnosed as PDD-NOS, they may be able to get wraparound services, ABA therapy, or whatever kind of therapy may help prepare your child for entrance into school and to help them socialize. Then, at school, your child may qualify for an aide, or speech therapy that will help with pragmatic language, or special ed classes, or the ability to take a longer time on tests, or a different room for tests, etc.
This can actually be a good diagnosis to have.