How to tell if a buzzer is passive or active?
Passive Piezo Buzzers run on AC only, no DC required. They're also often not called 'Buzzers', but rather 'Transducers', 'Elements' or similar.   

Active Piezo Buzzers run on DC, and usually the frequency they produce is specified.  

The one you link to is, without a doubt, an active buzzer, whereas this one is a passive transducer.