Throtle body
 

hey what does a throttle body do ???

Most throttle bodies go something like this:
A throttle body is simply a valve. There is a spring-loaded plate inside called a "butterfly valve" that opens when the throttle is pressed (via cable). That allows air to enter the motor.
Here is a quick little definition, best I could find.
http://auto.howstuffworks.com/fuel-injection2.htm

-Ducky