WiFi use Kindle and iMac

I have had my computer about a month now details as follows
imac,intel core i3, I know the mouse and keyboard are wireless and I intend to buy a kindle ebook reader will the kindle interact with my computer wireless or do I need to buy some piece of equipment for it to do this,it says the kindle is wifi and if my computer is wifi I can download books without connecting it to the computer via usb.
regards ray

Moved to correct forum. Title edited for clarity.

You buy books via the Kindle directly or from Amazon.com and they're downloaded directly to the Kindle, you don't need a computer.

I am not buying the 3g just the wifi edition.

You will need to have a wireless network setup or use a wireless hotspot.