I keep seeing “affiliate marketing” everywhere, but how does it actually work?

Lately I’ve been noticing people talking about affiliate marketing in videos, blogs, and even random social posts. At first it just sounded like another online trend, but the more I looked into it, the more I realized it’s actually a full system behind a lot of content I already see every day.From what I understand, it’s about promoting products and earning a commission when someone buys through your link. But I still don’t really get how people build traffic in the first place. Is it all about content, or is there something else going on behind it?