Diode driver has both variable output voltage AND variable current?

I am trying to purchase a TTL compatible driver for a m140 2w 445nm diode, and any help would be much appreciated as I am new to laser building and this is my second build after killing another diode due to improper handling of the driver and module connection.

I found this driver and it confuses me. It (and a few others i have found) seems to have variable output current and output voltage
acording to the pictures and labeling.

12V TTL 1W 2W 3W 445nm 450nm Laser Diode LD Driver Power Supply Stage Light | eBay

I have seen the usual constant current based drivers, but I have no experience with ones with variable voltage and variable current in the same circuit, and I have no Idea how I would set the voltage.

1. Is this normal or should I find another TTL driver for my M140 diode?

2. How would I go about setting up this driver? (I have a 10 diode variable test load from Survival laser and a multimeter to do so, but i only know how to use it for current check)

Also here is the diode I will be purchasing
http://www.ebay.com/itm/170898388161

I plan on using this for a CNC Laser engraver/cutter.

Thanks!!

EDIT: is the variable output voltage for the fan maybe?

(posting in Drivers section) but I dont know how to delete this thread