There's a heap of these questions, so before you mark mine as duplicate I'll try and explain how mine is different.
I don't really know too much about voltage and current, wattage, resistance or ohms.
If I supply my Pi with a computer power source, versus a wall charger, how is its needs met? Will it continue to draw until the power source breaks, or will the Pi be under-provided? What if the power source is too great? I understand too high in voltage will destroy the device, but what about too high in current? Will it draw what it needs (which seems to be suggested everywhere (and also makes no sense to me)) or will it break?
I'm probably the most confused with LEDs and drawing energy, because multiple sources say a resistor is in place to protect the Pi, and not the LED. To my knowledge, a resistor is because the current coming out is too high, but posts I've read talk about too much demand on the GPIO pins. What does that mean? Does the Pi try to provide the energy and can't (breaking the Pi)? or is the LED provided with too much current (breaking the LED)?