An Action is a play typically performed during an entity's Action Phase. Actions usually include one or more targets. An Action played against one or more enemies is considered hostile (and an attack) unless otherwise specified and permits a Reaction play from each targeted enemy.
Actions with the Area Effect keyword target all entities within one section, region, or position except as otherwise specified. Actions from Environs target all PCs in their occupied region unless otherwise specified.
If an entity plays a hostile Action of its own volition that targets itself or an ally, the target's Reaction loses any text and entries apart from Evasion Dice and Defense. In other words, an entity cannot decide to “attack” itself or an ally specifically for the purpose of granting an advantageous Reaction play. The DM may also prevent such plays from triggering other beneficial effects, such as from abilities or Assists. This even applies to Area Attacks that also target enemies. However, it does not apply if the entity was forced to play the hostile Action by an enemy.
If a target of an Action cannot play a Reaction, or if either the Action or Reaction played lack an opposed roll entry, the Action automatically succeeds and takes effect. Otherwise an opposed roll is performed to see if the Action takes effect.
For more information, see Player's Guide Chapter 3: Scenarios.