Mint
No flaws whatsoever. This grade should never be use with used records and most new records will not deserve it either.
Near Mint
Virtually flawless, not perfect. A minor scuff and the flaw should be very hard to see. If an imperfection covers more than a few tracks I will rarely give it a record a near mint grade.
Very Good Plus:
A 'Very Good Plus' record shows cosmetic scuffs and hairlines. Particularly in hard light. Some flaws will be noticeable to the naked eye, there should not be too many. Gloss should be very strong. No imperfection should be textured enough to feel with a finger. Such textured imperfections are called 'feelies'.  This record should play with little to no noise. The odd bit of static might just be dust.
Very Good
A Very Good record will look played, and show numerous cosmetic imperfections. It may still play very cleanly but the cosmetic marks should be noted. A 'very good' record may also appear to be very clean while playing with frequent noise or crackle or. A record that is in excellent (Near Mint) condition with a single 'feelie' audible imperfection usually falls into this grade.