How does a vanishing edge, or infinity pool, work?

A portion of the pool wall near the top or at the coping level (an absolutely level portion) has been removed and the pool fills up to that level and overflows. There is a catch basin on the other side where the overflow water collects. Using properly sized pumps and hydraulic design, the water is pumped from this catch basin, back to the pool which causes the overflow to continue the cycle. The “feed” of water to the pool can be another water feature (a natural looking stone waterfall, a “sheer” water feature), or something invisible from under the water surface.