Questions about SLI?

Okay I read the 101's and I am NOT understanding SLI.



Whats the prongs on the top of my GeForce 6600GT for? They look like the prongs that fit into the PCIE slot only much less / smaller.



.....How can you run two identical cards, with only one slot on the mobo?



Why do some power supplies say 'nVidia SLI ready ?'



Why does my mobo have a 6 pin SLI connector? It has nothing to do with the video cards?



Why doesn't my power supply have one?



Thanks

The prongs on top are for an SLI Bridge.



To run SLI, you need an SLI motherboard, which has 2 PCI-E slots.



Because they are designed for an SLI system.



If you had an SLI motherboard and 2 cards, then you would need that.



Didnt you just say you had one?