Some GPS questions

[xdestron]

So I noticed 2 GPS options on my Droid X. They are:

1. Use GPS satellies
2. Enable Assisted GPS

First of all, what is the difference between these two options, and second of all, can I be charged extra for its use with an unlimited data plan? The second option says something about "preferred service" so I am a little scared to use it because I don't want to get gouged on my bill.

Thanks in advance.

 

[Tangent]

Assisted GPS uses Cell tower radio signals to cut down the time it takes to narrow down your position. It should make no difference on your bill.

Assisted GPS - Wikipedia, the free encyclopedia