> -- Brett

...and since this was a pretty basic question let me focus on just one
difference between the two chords:  the half-step between the dominant 7
and the major 7.

The word major in that chord's name indicates that the seventh note in
the scale is raised a half-step over the same chord without that
designation in the name.  Same applies with a Major 9th chord - the
seventh is again a half-step higher than in a plain 9th

Frank