you use a b&w image for the displacement map. The back areas would make a valley and all that is white would be the tip of moutains; all the gray is somewhere in between.
So if you turn that image that you have to grayscale, and then assign the file to a materials displacement, and then assign the material to the plane, when you render the pane it will look as if you had modeled the mountains and sutff.
A displacement map is "like" a bump map, except that it actually changes the geometry (so you use to for "Bigger" bumps than just bump maping.
There can not be Good without Evil, so then it must be good to be Evil sometimes.