it attaches to your steering column, or front fork to your frame on older bikes.
it has oil and a piston and you can adjust the rate of which oil flows around the piston which gives you a softer or harder steering so in turn you can get better handling at higher speeds to your liking,,,, basically reduces the impact of hitting a pot hole mid corner at the handle bars.
the newer bikes have a speed controlled dampner fitted, that makes it harder to turn the steering the faster you go, where at stand still its as easy of if its not there
hope this helps mate
cheers Tim