Uh, you bought it and hooked up and don't know what its for? its to connect up to 4 Composite/S-Video Devices to your TV at once without swapping cords, just pressing a button.
The product comes with a manual (it's a bit confusing though). I googled the product and set up info, the directions were right there and very easy to read!
Just hook up your devices (i.e. game systems) into the inputs, and run a yellow white red cable from the output (either one) to the input on the tv. it is really not hard at all.
No, this product does not allow for switching from S-Video to RCA. This I'd simply an A/V switch amongst devices producing and receiving the analog RCA signal.
The products below may work for your needs. Hope this helps
Products from my answer
C2G - Value Series S-Video/Audio to RCA Adapter Cable - Black
C2G - Bi-Directional RCA to S-Video Adapter - Blue
Nyrius - NSW500 All-in-one HD 1080p Video Selector Switch,6-input,supports HDMI,VGA,Component,RCA & S-Video