Action, move and attacks.

Every round of combat, a character is limited to what they can do. Character's can only perform one action and one move per turn. The amount of attacks a person can perform is decided by their weaponry.

Actions:
Anything that is not classed as dodging, moving or attacking is classed as an action. Generally actions are defence based such as parry, taking a healing item or changing weapon. Psychic powers are classed as actions (even the offencive ones.)

Move:
Moving is classed as evading, moving to cover, or any such movement that effects the way of battle. Simple movements such as raising a gun or turning on the spot do not count as moves, and you're free to bulk up your posts with as many minor movements as you like.
Note: The average person can move six feet a turn.

Attack:
An attack is classed as the use of a weapon to attack a target. The number of attacks a character gets are based on their weapons. A melee weapon always gets one attack per turn. If the target is dual weilding melee weapons then they may attack with both weapons each turn, thus they will get two attacks per turn. Ranged weapons have a different kind of attack rate, and the ranged weapon overview should be consulted for more information.