Cavalry can move up to 6" in their movement phase. A unit of cavalry can charge 12" in the assault phase if it is within 12" of the enemy. In other words they move at the same speed as troops on foot, but assault twice as far. Cavalry mounted on particularly exotic beasts might charge faster or slower than this, where this is the case it will be noted in their description.
Cavalry are affected by terrain in a different way to infantry, being likely to either plunge through it or fall prey to a mishap rather than be delayed. So if cavalry enter difficult terrain roll a D6 for each model. On a 2-6 the model rides through any hazards unscathed, on a 1 the model has a nasty accident (eg stumbles in a pothole, rides into a low branch) and is removed as a casualty. No armour saves are allowed.