My unscientific translation guide:
"Blazer" - get that thing graded!
"Nice" - sell it to someone who thinks they know more than you. They'll pay to get it graded
"Mid-grade" - stick it in a binder and enjoy the damn thing
"Collector grade" - Don't be afraid to handle it raw. OK to leave out loose on your desk overnight...unless, of course, you have a cat.
"Well-loved" - if you squint, it looks fine. Don't worry, it will look better as you get older and your eyesight begins getting worse
"Beater" - still more or less complete. Its road map of flaws probably tells a vaguely interesting story
"Ouch" or "Ooof" - at least it's still a card...kind of