Movement speed is quite simply one's speed of running. The higher the movement speed the faster one can run. Fast speed is advantageous when trying to tank mobs because you can run from them and so take less damage. The movement speed is limited to 200, if you have more than 200 it will be useless because you won't go any faster. Spirit Stone of Hatse can increase your characters movement speed. If any of your characters have Speed of Wind, Beserk, or Dance with the Wind skills, it will give you more movement speed.