Rush

From The StarCraft 2 Wiki

A "rush" is a general tactic in a StarCraft/StarCraft I game which is based on making a few units very quickly to kill the opponent before he or she has mounted an effective defense. In some cases it can be beneficial to use all the initial workers and go kill the workers of the opposing player, but usually not. A "rush" can also involve a Protoss player building a Pylon and Photon Cannons near or in the opponent's base.

The purpose is to wipe out or inflict heavy damage on your opponent's start, giving you a serious advantage or even a possible victory within a few minutes of the game's beginning. This is very effective against enemies who were planning only to invest lightly in the early game Tier One while racing to higher and more powerful units up the Tech Tree. Be careful however, prepared defenses such as a garrisoned Terran Bunker can destroy a attempted rush; thus causing the tactic to backfire as you have now lost more than the enemy. Rushes are not without risk and can fail just as often as they succeed.