Also, the writers of all these ARM documents are experts, so they occasionally don't take the time to define and explain the most simple basic things. It's part of the human condition that once you become an expert at something, you forget what it was like to be a novice, so you can't remember that novices need to know the "novice" things first. Expert teachers think differently; they remember what it was/is like to "not know," so they explain things from the ground up.

I ran into the same problem reading the "ARM® Cortex®-R Series Version: 1.0 Programmer’s Guide." It's crazy, but yeah, they don't explain these terms either in that document.