Final answer:
USB 2.0 devices must exceed 100 milliamperes to be considered self-powered, which means they have their own power source and are not limited by the USB port's power capacity.
Step-by-step explanation:
The power threshold that USB 2.0 devices need to exceed in order to be considered self-powered is 100 milliamperes (mA). A USB 2.0 device is considered self-powered when it does not draw power from the USB bus and has its own power source, like an external power supply or a battery. This designates that the device does not rely on the power provided by the host device's USB port to operate, allowing it to potentially provide more functionality without being limited by the USB port's power capacity.