I must not of understood something. Online, I've heard that the Arduino uses 9v typically (average), and that USB's in general supply 5v@500mA. If this is true:
1) How can the Arduino even POWER ITSELF with the 5v USB? I've heard the minimum is 7v.
2) How can there be a 5v pin if the USB supplies 5v... that leaves no room for the Arduino!

My understanding is very bad currently, any explanation would be great. Thanks!

I must not of understood something. Online, I've heard that the Arduino uses 9v typically (average), and that USB's in general supply 5v@500mA. If this is true:

1. How can the Arduino even POWER ITSELF with the 5v USB? I've heard the minimum is 7v.
2. How can there be a 5v pin if the USB supplies 5v... that leaves no room for the Arduino!

My understanding is very bad currently, any explanation would be great. Thanks!