Turtle: The more defensive strategy. You mostly only focus on defense here and try to create an impenetrable base well... fortress. Turtles forget about offense and wait for the enemy to attack, once they attack (and hopefully fail) and attack again AND fail they eventually rage quit and by default you win.
Cheese/Cheesing: The forceful strategy. Doing this you expand your base closer and closer (or create a new base) towards to, next to, or maybe even in the enemy base. Most people just spam defense structures next to an enemy base to demolish it.
Booming: The business-sided strategy. When u boom all u want is resource, resource and oh i dont know, more resource. Boomers (not the L4D zombies) just want money cuz money makes the perfect offense and defense... right?
Raiding: The economical offensive strategy. When you raid you send small packs of units to attack here and there, yes this is very useful, while u try to establish a fairly good base you can keep the enemy busy with your small attacks.
Rushing: The cheap, hard, fast strategy. Who cares about defense? who cares about resource? If you both start of the match with nothing but workers and if you can create a massive cheap army within 10 minutes and attack you should win... Theoretically. While the enemy is to busy making a base you just create your cheapest units to attack them straight away. In the beginning of a match everyones a sitting duck!