There's a lot to it, but I see Tim Ford has a nice blog post on what it means to be a professional.

While I agree that we want to continue to learn and share what we know, I'm not sure it implies that we definitely know what we are doing. Rather I think it means that we strive to use best practices, we strive to constantly do a better job with better being defined as something of higher quality than a layman would achieve.

And to me that means that the PASS Summit, SQL Saturday, and other events are a part of a professional's lives. Not all of them, but some of them. 

You don't have to try to be a professional in all aspects of your life, but in your career, I would hope that you would.