Movement is a character stat needed to move around the mud and perform certain actions like combat skills.
As you move from room to room movement is deducted based on the terrain. If the required movement would become less than zero than the player will be unable to move.
Movement is also deducted for other things like recalling, sending messages too rapidly, or spamming commands.
Movement is also a possible effect on a piece of equipment. The movement effect increases your maximum movement.