This feeds your CPU, Mainboard, RAM and the HD 5570 itself, because it does not need another cable plugged in.
Then your PSU has other cable(s) like this:
That feeds the HDDS and drives. I am pretty sure your PSU gives 10 amps at 12 Volt on these wires, but more on the first mentioned.
Edit: Open your case and have a look on your PSU: There should be the name of the brand and the type on it. Google that and you'll find out exactly.