Gapping basically means the amount of yardage you have between a full swing with each one of your different clubs. Your full set of irons are naturally gapped because the loft differential between each iron is more or less uniform, but when it comes to your wedges, it becomes even more critical because of the onus on those scoring clubs.
Ideally, you’d like about a 10-15-yard gap between each one of your wedges, which should more or less be consistent with the gapping between your other clubs. This ensures that you’re never trying to hit a club too hard or too soft, especially as you get closer to the green.
Begin your gapping by knowing what degree your iron set’s pitching wedge — or highest lofted club — is. From there, you want to ensure the next club has between 4-6° more of loft, continuing throughout the rest of your wedges.