system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Can someone explain what wind is?

Where does it come from, what is it?
gpt
Some parts of the Earth's surface are hotter than others. The air above these bits rises, because it's hotter than cold air. This leaves a gap under the rising air, and something has to fill it, so colder air gets sucked into the gap. This happens on a *huge* scale, and is fundamentally how wind works.