When reading about the electrical needs of various electronic devices and/or appliances, I often see a requirement for only one of the various measures related to electricity. For example, it will say "requires 120 volts" and not mention anything about amps. Or it will say "takes 10 amps" but not mention anything about volts.
Here is just one example from Lifehacker, in an article about the Raspberry Pi:
A power supply: The Raspberry Pi is powered by a micro USB, much like the one you’ve likely used for your phone. Since the Pi 3 has four USB ports, it’s best to use a good power supply that can provide at least 2.5A of juice.
Isn't a statement like that useless? There is no mention of required voltage. 2.5 amps can be delivered in many different ways - i.e. by 5 volt pressure, or 240 volt pressure. I suspect this can produce very different outcomes.
So why are volts and amps often given as though they are completely independent? Why would there be an explicit requirement for one and not the other?