You have heard of Appaloosas right? Tiger horses are a breed... but they carry the same coat patterning that Appaloosas do... and Appaloosas are much mess rare. You mentioned a reservation... Indian reservation I assume. Reservations breeds lots of Appaloosas... in fact... usually ONLY Appaloosas. I have a friend with a registered Appaloosa mare who has a few mares in her pedigree who are simply named "reservation bred mare". If you horse is an App., which I FIRMLY believe he is... he is a "fewspot" App. That is a pattern... it also happens to be a pattern that is "homozygous", which means if he was bred, he would ALWAYS produce foals with a pattern. It also means he had to have two Appaloosa patterned parents... leanding credence to my argument. The color of his hair and skin, eyes, ears, etc... they all point to him being a fewspot. Here: take a look at this: http://palisadesapps.homestead.com/dreamindun.html
Foundation bred means that the horse has been bred from very limited lines and trace back to only certain horses in the breed. It's very important to the future of the breed to maintain some of the characteristics the original horses had, and foundation horses assure that.