Grip Tape
Grip Tape is basically sandpaper that has a peel-off sticky paper backing that you stick onto the top surface of your skateboard. This creates the grippy surface necessary for maximum shredding. The coarseness is determined by a numbering system that states the amount of particles per square inch of tape. This is know as the "grade." A lower number indicates a coarser grade and a higher number is finer. Most grip tapes don't list the grade anymore, so you will typically see it listed as Coarse, Medium or Fine, if they list it at all. Coarse is suitable for downhill racing or vert. Fine or Medium grade grip tape works best for freestyle; mostly because you don't want any unnecessary friction hindering your Bitchin' footwork, but your shoes will also last longer.
Many freestylers also put grip tape on the bottom of their boards, under the Nose and Tail, to help prevent their feet from slipping off, when doing Caspers.
