Trademark vs. Copyright vs. Intent?

So what's the difference?

I know domain names can't contain trademarks, but what about product names? Are those usually trademarked or off limits? Model numbers?

How about people's names?

Has anyone been sent lawyer letters over their domains on here? I'd like to hear the details!

This has been hashed out here dozens of times. It is almost certain that a product name will have a "mark" of some kind. uspto.gov is the place to check
People have been sued, receive c&d's etc.