Most of the time, game play is relaxed and casual. The GM sets the scene, and players take turns describing what their characters are doing. When the situation calls for it, the GM has the players make die rolls (skill checks or attribute checks) to determine the results of their characters' actions. But when a scene involves combat or the imminent threat of combat, a structured sequence of combat rounds governs play.
In a combat round, each character gets to do something. A round represents about six seconds in the game world, regardless of how long it takes the players to complete the round.
At the start of a battle, each player makes an initiative check for his character and the GM makes initiative checks for the opponents. The character with the highest result acts first, followed by the other characters in order (from highest result to lowest result). This order of play is used in every round until the battle ends. When your turn in the order comes up, you perform all the actions you are entitled to in the current round.
There are four types of actions: attack actions, move actions, full-round actions, and free actions. In a round, you can do one of the following things:
An attack action lets you do something. You can make an attack or perform an attack-equivalent action, such as using a skill or talent (except those skills and talents that require a full-round action). You can perform an attack action and a move action, in either order, in a combat round. You cannot use two attack actions in one round, however.
A move action lets you move your speed in a round or perform a move-equivalent action. Move-equivalent actions include climbing, drawing or loading a weapon, opening a door, or picking up an object. You can move and attack, in either order, in a round. Or you can perform two move actions in a round, using a second move action in place of an attack action.
A full-round action consumes all your effort in a round. Attacking more than once (if you are of sufficient level to do so) or using a skill or talent that requires a full round to employ is considered a full-round action.
Free actions consume no time or effort. Over the span of a round, the impact of these types of actions is so minor that they are considered to be free. Speaking to an ally or opponent, dropping an object, or activating a simple device like a flashlight are all examples of free actions. You can perform a free action in addition to performing another action in a round, though the Game Master can place limits on how much you can reasonably do for free in a given round.
Some rolls, such as saving throws, are instant reactions to specific events. Likewise, some skill checks are reactions, such as making an Awareness check when the GM calls for one. A reaction takes no time and isn't an action.