Swimming pool sand usually refers to pool filter sand, used inside a sand filter to clean and purify swimming-pool water.
Pool filter sand
Removes dirt, dust, algae particles and other impurities.
Goes inside a sand filter tank, not directly into the pool.
Commonly uses specially graded silica filter sand.
It should be the correct grain size specified for the filter, often around 0.45–0.55 mm.
The sand normally needs replacement after several years, depending on use and water condition.