Hello again Albertocheets,
Sorry the explanation above did not satisfy. Here is another angle on what an augmented chord is:
In the song you are learning, the chord progression is G - Gaug - C.
In this case the Gaug is used as a way of making the transition from G to C more 'interesting'.
Here are the notes in each chord:
G = G B D
Gaug = G B D#
C = C E G
This series of chords has a nice chromatic (1/2 step) sequence (D, D#, E).
This little line of notes is subtle, but it makes for a very pleasing effect.
Augmented chords are often used like this.
Alone, augmented chords sound a little 'off', but used between 'regular' chords they work nicely.
As Roger Guppy pointed out, the song was originally composed by Carole King and Gerry Goffin. These two composed mostly at the piano. Consequently, they often use chords that may seem unusual to guitarists.
"That darn Pythagorean Comma thing keeps messing me up!"
[url]http://en.wikipedia.org/wiki/Pythagorean_comma[/url]