The letters DSM stand for "Diagnostic and Statistical Manual". The full name is "Diagnostic and Statistical Manual of Mental Disorders".
The DSM is a Diagnostic tool for neuropsychologist. It describes Observable Behavior. Psychology on cop shows and sitcoms is about knowing how people feel or think. The DSM is very much in the school of Behaviorism. It is NOT about It how people think or about how people feel. It is about how people behave. Observable Behavior.
It uses jargon (sometimes).
Onelook.com can help with the jargon. When I am reading technical papers or books from a field I am not familiar with I look at Onelook first. I do not read the definition from only one dictionary, but I read from 10 or more dictionaries and try to decide which definition most makes sense in the context - and the DSM context is Observable Behavior.
Another trick for decoding jargon is to do a search with google using the word you want a definition of, the context (Psychology) and the special key word "glossary". Sometimes a jargon word will have a Wikipedia article, which is useful for getting general context, but should not be taken, itself, as authoritative.
acronymfinder.com is another useful resource.
Two things to be aware of with DSM jargon: in some cases it may use words that you have never heard before. In other cases it uses words you think you know but they don't seem to make any sense in the context they are used - this is because there are special definitions in use in the context of neuropsychology/Observable Behavior. Not thinking you understand a jargon word because it is used commonly in English is important.
The purpose of the DSM is to help make a diagnosis. It is supposed to be used by a trained professional - who is familiar with the context and is also a trained observer, and is familiar with the jargon.
A Neuropsycologist or a Psychologist may be a doctor, that is a PhD. A Psychiatrist is a medical doctor, a MD. Some DSM diagnoses may result in medication being assigned by a Psychiatrist or a physician who can write prescriptions, but is not a Psychiatrist (such as a general practitioner or a pediatrician) but the DSM does not talk about medication, it talks about Observable Behavior use to diagnose one of the named (and numbered) conditions. The DSM is used in the USA. In Europe they would use the ICD-9 or ICD-10. ICD stands for "International Classification of Diseases".
A neurologist is a doctor who in concerned with the nervous system. He would not typically use the DSM for diagnisis, but he might use DSM diagnosis as a criteria for selecting subjects for a neuro-imaging study (such as a MRI or FMRI study).
In the DSM-V (version 5 of the DSM) the Autism diagnosis added (for the first time) quantitative measures, that is the ability of the person making the diagnosis to assign a number (or quantity) to two specific diagnosis criteria. These may be numbers, but they are still tied to Observable Behavior. A rubric ( a small table with numbers and short phrases or paragraphs to describe the type of behavior that qualifies for that number) is provided in the DSM-V.
I have a copy in PDF someplace - I will have to dig it up to give more detail.
_________________
ADHD-I(diagnosed) ASD-HF(diagnosed)
RDOS scores - Aspie score 131/200 - neurotypical score 69/200 - very likely Aspie