What exactly does it mean that the N810 has USB 2.0 OTG ("On-the-go")?

Will that mean that has USB host capability? Can you plug a usb keyboard into it, for example? What about a USB flash drive?

Also, do you think it is possible that OS2008 will bring OTG capability to the N800, or is it a hardware difference?

(I don't have a NIT at this time, but I'm considering the N800 now that the price has dropped so much. I liked the idea of the sliding keyboard, but can't see spending almost $500 on the new device. I rarely drive, so the GPS doesn't add value to me, though I can understand its appeal to many people)