Thermaltake case connections

[knucklebones]

I'm just building a new system and have a thermaltake Tai-Chi case.
My question is about the 'icage' hhd bay. It has 2, 4pin power connectors and 1, 3pin connector. the 3pin has only 1 wire going to it, and it looks like a mobo connector. Do both of these 3/4pin connectors have to be connected?
or is the 3pin just for the LED?
Thanks for any help

 

[Septh]

The 3 pin one goes to the mobo to show you the fan speeds then the 4 pin molex goes to your psu to power the fan ands light

 

[knucklebones]

Thanks for the help.
Been awhile since I built a PC.
What's the reason for the two molex connectors per fan?