system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is a "ground wire" and why are they important/used?

I know modern electrical receptacles have three wires - hot, neutral, and ground. What is the ground wire and why is it important? Is it there for safety reasons? Does it help the device drawing the power in any way?
gpt
Electricity flows out of the hot, through the wires in the device, and back into the neutral.  If the device has a metal casing and a hot wire comes loose and touches the metal casing, the metal casing is now also hot and if you touch it the electricity can then travel through your body.  The ground prong is used to ground the metal casing so that if a loose hot wire touches it the electricity flows directly to the ground instead of you.

edit: The neutral and ground prongs are both grounded (lead to the ground).  They just take different paths to get there.