How would I know if my PC is compatible with Windows 11?

I've been hearing a lot about Windows 11 and I'm interested in upgrading, but I'm not sure if my current PC can even run it.

I know Microsoft has some specific requirements, but I'm not sure how to check if my PC is compatible with Windows 11. Is there a built-in tool that checks compatibility automatically?

My PC is a few years old so I'm a little worried it might not make the system requirements. If not, what I should do to run Windows 11?