6pool is a StarCraft II zerg rush strategy. It centers on building a spawning pool before anything else. This is roughly the equivalent of StarCraft's 4pool in that it similarly focuses on building a spawning pool before anything else.
Set the hatchery's unit rally point in the enemy base. The main objective is to destroy workers and cripple the opponent's economy.
Terrans may wall off a choke point and prevent the zerglings from getting into the base.
During a forge expand the protoss must give up their forge and pylon on the low ground and build a photon cannon in their mineral line slightly closer to one of their assimilators and begin building a gateway.
It is difficult for zerg to wall off against 6pool. Instead, build spine crawlers next to the hatchery and build zerglings.
6pool is less effective on maps where there are more starting positions than players; time spent "attacking" empty starting positions is time the enemy has to prepare.
6pool is stronger on maps with wider, and harder to wall off, base entrances. This forces the defender to rely on unit and defensive structure production to stop the rush.