USB-C is the currently adopted specification for the USB protocol. Everything uses this now, because it extends on the base functionality of USB-A and MicroUSB, like with Thunderbolt.
Power negotiation
USB-C is special as a power delivery standard because it automatically includes a feature called power negotiation.1 Because USB-C has seen widespread adoption and because it can support a wide range of power delivery needs, there’s an obvious consideration on whether a charger rated for a high wattage won’t fry the electronics on your smaller device.
Both source and charger devices have controllers. When attached, the controllers will communicate with each other what their power needs/discharge capabilities are. In the case of smaller electronics, their controllers will communicate to the charger that they can’t support a higher voltage/current. The charger will meet the needs of the device.
Footnotes
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Derived from this article. ↩