Completion Actions
Completion Actions are the actions to take on the record when this trigger is completed. This is not used very often because typically you use the User Buttons section to set values on the way out of the trigger. However, there are cases that no matter which button is clicked you want to be sure to call a specific action. If that is the case then you would use an Outbound Action.
Actions
These actions are outlined in the Work Trigger Action Types section.