Type of Action: Full attack action (a standard action + a move action)
A character can walk twice its listed speed by performing a double-move. This is usually done by converting the character's standard action for the round down to a move action, and then using the character's move action to walk again. Note that a double-move is treated as a single action, so there is no need for the space between the two move actions to be unoccupied, though the character must (obviously) still be able to move through the space legally.
Like walking, a double move is a cautious form of movement, though it still provokes attacks of opportunity if you leave any spaces threatened by enemies. Because it is counted as a single action, you can only be the target of one attack of opportunity per enemy creature you provoke, even if you leave multiple spaces threatened by the same enemy.