Brandon:
There are several ways to answer that question, but, in short a blower is used to raise compression and increase airflow into the combustion chamber. With the blower that I believe you are referring to there are two aluminium "gears" that look similar to that curly mac-n-cheese. They fit fairly tightly together so that when they spin at high speeds they will suck air through the unit.
These pull air in through the carb, (or throttle body) and down into the motor. One simple rule of horse power is, the more air that you can get into and out of your motor the more power that you can produce. Could give a tech talk about the pounds of boost equating to the compression ratio and that low compression pistons and high boost is the way to go but .... I run a blower on my Harley! Instant on power!