The 94 VFR might not have all of these adjustments on front and rear. Damping keeps the bike from behaving like an old Cadillac - i.e., still bouncing 10 seconds after hitting a bump.
Compression damping slows the shock when it is being compressed.
Rebound damping slows the shock when it is rebounding. PVC pipe works well. Start at the shock manufacturer's recommendations. Only change one setting at a time, and don't change damping more than 2 clicks at a time. For compression damping, increase until expansion joints or sharp bumps are jarring, then back off one click.