I'm reading the second chapter (Transidtors) in the Art of Electronics and I found a sentence that I couldn't make sense of.
Note that voltage amplification isn't what matters, since, for example, a step-up transformer, a "passive" component just like a resistor or capacitor, has voltage gain but no power gain.
It says that a transformer is a passive component that has voltage gain. A resistor or capacitor are also passive components. Passive components never have power gain.