What does defog do in diamond?

Answer 1

in the great marsh rite after u enter through the front you will see 2 people im pretty shure ether way just talk to the guy on the right and he gives it to u this could be how u get it in pearl but try it anyway

Answer 2

if you teach defog to a pokémon, it will have the ability (strangely) to clear the fog. You know, like in caves, it will make the view much clearer. In battle, as you can probably guess, it is pretty pathetic;)

Answer 3

It makes fogs go away. So if u go to a fogy place like route 210 u cn clear the fog wth defog