Redbook is the standard that Philips and Sony came up with for the spec of CDs. Including length of playing time. Around 650 MB, I believe. The 700 MB ones aren't Redbook, technically. Usually can be read on a Redbook conforming unit, but that leaves them an out if it doesn't.
PRAT means "pace, rhythm, and timing". Commonly believed to have its origin with NAIM fanatics, as a way to describe how well it does (or doesn't) achieve some imaginary audiophile quality. IOW, some nonsense they concocted to differentiate its performance, relative to other brands. Not much in favour on the US side of the Big Pond.
