Whenever a character decides to "do something", they are taking an action. Many actions can simply be declared by the character (the player or narrator) and their obvious result occurs. For example, a player can say "My character sits down at the bar.", and, unless the narrator provides a reason why this doesn't happen, it can be assumed that it does.
Many actions, however, require a check to see if the action succeeds or fails. Any action whose success is in question will require a check - if the action is opposed, or difficult, or requires some degree of luck, the narrator may decide that a check is required. Should the check pass, the action and its intended result occurs; should the action fail, the result does not occur, and, at the narrator's discretion, may have adverse side effects.
Actions that require a roll are defined either in the various skills available to all players, or as talents in the various tales that characters can unlock. These action entries will specify what check the character should make, what the outcome is expected to be, and if any additional effects can be added on or modified (such as with the demonstration of virtues).
As an example, consider the following talent:
In addition, many actions that have a fixed mechanical effect in the rules, but do not require a roll, are still defined as above (but without the check specification). For example, Stabilize, an action found in the Medicine skill is defined as:
Some actions are restricted in the number of times they can be used. This restriction is worded like: "once per encounter". In any given encounter, the action cannot be used more than that many times for a given character. If such an action is used outside of an encounter, those usages count immediately and last through the end of the next encounter.