G+7 is a G7 with a raised 5th or G aug 7. But sometimes the notation is wrong. I was always taught that it was an augmented chord by my professors. But I've downloaded some chord progressions from internet web sites that have the same type of notation (G+7) but they actually meant G Maj 7.
This is usually a problem when the notation comes from a person that originated from outside the Unites States. I find it mostly in Brazilian music. So in that case you would have to listen to the song and try the chord to see if it fits.