ok rawhide is literally raw hide, that means its been fleshed de haired, salted and dried. It has not been tanned.
buckskins is a word used to describe tanned deer hides.
I will recommend before doing anything else buy the book "deerskins into buckskins" it will tell you everything you need to know about brain tanning and explain everything very clearly.
my son and myself tan our hides and bought the book a few years ago it is a godsend. don't listen to anyone else or read anything on the net, just buy the book and follow it. the problem is there are few ways to do things and this book explains each one without confusing the issues.