How to earn money on Steam?

I've heard that there are ways to earn money on Steam, but I'm not entirely sure how to go about it. Can you give me some insights on how I can start earning money on this platform? Is it through selling items or games? Or is there some other method that I'm not aware of? I'm interested in learning more about this and potentially leveraging it as a side hustle. Please provide me with a detailed explanation and any tips or advice you might have.