First off i know theres a name that chord forum, but i hate giant generic forums so here's my dilema

In the real book I've come across chord symbols like this G-7 and G- and two bares later it will say G7 so I know that its not a regular G7.

Idk what it means...please help

'-' or 'm' is minor.
A letter on its own is a major chord.
A 'M' before an extension usually means a major chord that uses a major 7th.
A triangle after a letter usually means a Major 7th.

Real books are mostly up to your interpretation of them. Some people take '-' as being a minor 7th and some don't.
G = Major
Gm = Minor (Sometimes expressed as G-)
G7 = Dominant 7th (Flat 7)
G followed by a superscript triangle = Major 7
G followed by a superscript circle then 7 = Diminished 7
G followed by a superscript circle with a line through then 7 = Half-Diminished 7
G- = Gm
G-7 = Gm7
Only play what you hear. If you don’t hear anything, don’t play anything.
-Chick Corea
G7 is G dominant seventh. G- is a G minor chord, and G-7 is a G minor seventh chord, but the changes (often the chord quality) in the real book are'nt great and the changes to a tune are subject to change on a gig anyway.