Actions per Minute (APM) is a measurement for the speed at which a user is able to interact with the game...
Actions include:
- Selecting units
- Moving units
- Launching attacks
- Setting research tasks
- Building structures
- Building new units
- Issuing repair or retreat orders
In short, any productive mouse click or keypress is an action. Thus an action can consist of several clicks / keypresses to deliver a productive result.