im new and have many stupid questions to ask

A sleeve is not a performance part. It is the cylinder the piston rides in. The only improvement a sleeve can ofer is by adding a big bore sleeve to your stock jug or by habeing port work done on it.

Edit:I need to learn how to type faster.lol.
 
^^That said, a big bore sleeve will significantly increase your displacement, and after other parts and tuning, your power level should go up. However, most people just buy a big-bore cylinder because all the aftermarket cylinders have better port designs and flow than the stocker, even one with a big-bore sleeve. Therefore, most people think of a sleeve as just a refresher type of part.