Rushing is the most common, and feared, tactic in the RTS genre. It's powerful and executed very early in the game, making it highly effective and feared.
Rushing is where a player in the match creates many units that are cheap and quick to create and then sends them to an enemy's base as quickly as possible. There are two outcomes:
1.) The rusher wins the battle and his enemy is defeated.
2.) The enemy manages to destroy the rusher's army and then the rusher is badly hurt for the rest of the game due to little or no resources and no units except for maybe a worker or two.