Always wondered what this hack does

Ok, just a question, I have always seen this feature in many hacks called "No Fog" what exactly is it's purpose? I mean I never understood what it does. Anyone mind telling me?

likke in snow valley..it removes the fog=easier to see
thank + rep me please

From what i have seen all it does ,is makes the map you are in clear

Ah ok. Thanks for the replies guys

go in snow valley match. Turn nofog on and off look in the sky.