You have the cards but are they legal to play with? For tournament play your card cannot have any marks on it so you could identify it just by looking at it's back.
Most card stores have their own grading guides, so far there is no one guide that everyone uses. In fact I used to have my own grading guide in my ebay store! Now days 95% of my cards are MINT or NEAR MINT, those that aren't I specify what is wrong with the card.
MINT - This card looks like you just pulled it from the packet. No marks or scratches - PERFECT! A person can keep cards in MINT condition by putting them into sleeves and playing with them.
NEAR MINT (or EXCELLANT) - This card can have a very slight wear, usually after someone plays with it but looks after it. The corners may be slightly worn.
VERY GOOD - This card has either been played with a lot or stored very badly; it may have a slight crease, the sides may be slightly worn with a little bit of the white card showing through or corners are worn.
If a card is graded above this line then it is tournament legal; if it's graded below then it's not allowed in a tournament unless it is in a sleeve. Note that a card can be MINT condition on the front but if the back has a mark on it then the judge may rule it illegal. As in all sports - Judges decision is final.
GOOD - This card has been played with a lot. It has marks on it or bent in half.
POOR - It's been through the washing machine by accident :( I have only ever sold one card like this and that's because of the artwork (the card was ruined but the Artwork was fine).