same as it works with active glasses on a tv. there is alot of info online about it.
basically the images on screen alternate from left eye, right eye, left eye etc. and the glasses black out the opposite eye. this happens really fast and makes your brain think it is viewing two different perspectives of an image in different eyes thus making it look 3d.
if you look at the screen without the glasses then the image will look blurry. with three monitors you may see the edge screens out of the corner of your eyes beyond the glasses but im not sure how much of an effect this will have
active 3d makes things darker than passive 3d (which uses filters on the lense and screen) that Nvidia kit includes software to make the screen brighter to negate this. active 3d should work on any screen as long as you have the software and glasses to make it work. passive 3d requires a special screen as well as the glasses.