At the start of a game you will need to have a look at the areas of terrain on the tabletop and decide how difficult they will be to traverse. Don't panic! There's a list of examples below. It's best if you can agree the terrain with the person you're playing against, but you can always roll dice for any areas you're not sure about.
Terrain is classified into three types: normal, difficult and impassable.
Normal. Grassland, crops, moors, most hillsides, streets, buildings, gantries, ladders, steps, fields, open woods, sparse brush or bushes, sand, rocky plateaus, craters, ice sheets, scattered rocks or monoliths, most ruins and low walls, most streams and rivulets.
Difficult. Sand dunes, loose ash or clinker slopes, steep hillsides, thick mud, dense or tangled woodland, thick vegetation, jungles, deep snow, marsh, peat bogs, waist-deep water (or other harmless liquids), unstable piles of rubble.
Impassable. Very steep slopes and cliffs, high walls, bottomless dust pits, geysers, lava, swamps, tar pits, sludge pools, toxic waste, very deep water.
If the dice roll is not high enough for the models to move into difficult terrain, place them just inside its edge. Any models in the unit which don't actually move in difficult terrain still get a full 6" move, but remember that they must form a continuous chain with the rest of the unit that is in difficult terrain.
Impassable. Can't be moved through at all unless the troops have special training, supernatural abilities and/or the right equipment. Where this is the case it will be noted in the troops' or creatures' description.