Combat
When every individual action counts, you enter the encounter mode of play. In this mode, time is divided into rounds, each of which is 6 seconds of time in the game world. Every round, each participant takes a turn in an established order. During your turn, you can use actions, and depending on the details of the encounter, you might have the opportunity to use free actions on your own turn and on others’ turns.
Activities in Encounters
Activities that take longer than a turn can’t normally be performed during an encounter. Spells with a casting time of 1 minute or more are a common example of this, as are several skill actions. When you commit to an activity during your turn in an encounter, you commit to spending all of the actions that it requires. If the activity gets interrupted part way through, then you lose all of the actions that you would have spent on that activity. Activities are described in full here.