I don’t personally know of any difference except as marketing material. I have used devices marked under both names, for both purposes. The only exception I can think might apply here is if you get a charger that has a surge rating – where it puts out a significant amount of power to force a rapid-charge. Anything suitable for powering a device will have a constant rate output, there is no internal circuitry involved like what is needed for monitoring rechargeable batteries (but that would likely be marked as a recharger or specifically as a battery charger, unlike a more generic phone charger).

Essentially what it comes down to is looking at how much amperage your device requires, and finding a charger/power supply that matches or exceeds this requirement. So like an older Pi worked with less than 2 amps, thus I have several 5V 2A micro-usb power packs laying around for them. It would work equally well with a 3A power supply or charger because the device itself still only consumes 2A of power. If I tried to use an older phone charger which only provided 1A of power, then the Pi would continually reboot because it wasn’t receiving a suitable amount of power. Make sense?

A couple conversions to be aware of… 1A (amp) = 1000mA (milliamps), so that’s an easy one. If you find a power pack that only tells you how many Watts it provides, divide that by the output voltage. So a 5W power supply that provides 5 volts will only give you 1 amp of power (5W / 5V = 1A).

Also note that a lot of Chinese sellers will provide an absurd rating for a given price, something like a 5A power pack for $8. What most people find when they open up these units is that the circuitry is barely even functional and more than likely to blow up the equipment you are trying to power. I tried one that measured fine on my multimeter, but as soon as I plugged something in the voltage dropped to almost nothing. These can easily be identified by being extremely light weight, for example something in a box the size of a laptop power supply but it feels like it is barely heavier than the plastic. Any reasonable power supply will have an obvious weight to it from the wire windings in the transformer.