It is the dispute resolution procedure written into the Federal Sp Ed. law since 1975 passage of 94-142.
If you read a "Parents' Rights Booklet" from many states, it sound as tho' this would be a reasonable thing to do if you had a problem with your child's special education. Of the 627 people who responded to the survey I did last year on this site, only 23 had been to Due Process. It is difficult and stressful--can be expensive, and often does not produce the desired result even if you win. It's a very bad system and causes far more litigation than it prevents.
However, it is the process that every parent of a child with an IEP in the entire country is stuck with.
Sheila may be able to direct you to links that will explain it in detail. I'm sure there is something about it on www.wrightslaw.com