Polymeric Sand is a polymer based sand that crystallizes and hardens when water is applied. It is very important to get excess polymeric sand off paver surface prior to wetting.
Paver Sand is just a medium grade sand that does not harden unless using Water-Based Acrylic Urethane with a bonding agent to harden sand (Seal-n-Lock Sealer or Ure-Seal).
ASTM (American Society for Testing Materials) & ICPI Standards (interlocking concrete Pavement Institution)