What makes a Tactical Light?

I see alot of stuff advertising tactical lights. I got a flashlight mount with my Mossberg 500 (who knows why, its a field/deer combo), and just to take a picture with it i grabbed an LED flashlight i keep in the kitchen drawer that costs $2 at the local CVS Pharmac. After looking at that light on the end it would actually work very well as a tactical light the only downside i see is that it runs on AA batteries so you would have to be aware of that and change them often enough they dont bleed out. The light is very bright and this particular one doesnt stay on (the guts are kinda loose) from being dropped on concrete too many times but before that it was a quality light.

So what seperates a fancy pants tactical light from a regular good flashlight, mounting hardware aside.