Triggers have flags that can be set to specify what entity type can trigger them. Check the box to select which entity type can activate the trigger. Any trigger defaults to allowing only clients (players) to activate them, but this can easily be changed to allow or forbid multiple activator types.

As an example, if you want a window to break if you throw a rock at it, put a trigger_once entity in front of a func_breakable entity (named window01) and set the flags of the trigger_once entity to Physics Objects only.

The output obtained for the trigger_once entity would be as follows:

OnTrigger, window01, Break, 0.00s delay

The window will break if any physics object, such as a rock, touches the trigger, but it will not break if the player touches the trigger.