Jack...yes, the seam guide is different than the 1/4" foot. It attaches to the post along with your 1/4" foot and has an "arm" that extends. It is adjustable and can be set at your 1/4", 1/2", and 5/8" markings on the plate. Instead of trying to keep your material on the lines (or tape, if you use that...I don't like anything sticky on my machine :)) the arm that extends keeps your material guided perfectly.
Hope this makes sense :)