General Question: Is it a support or a mage?

Is there a way to determine why some champs are support and some are mages? I.e. Is there a defining characteristic? Lux is a mage, but but Lulu is a support (iirc) and I'm referring to their Champ Mastery here, not if they're listed as a Main/Secondary. I support with Maokai often. But I'm still a "Brute" in my masteries. He's a little more straight forward, but the mage/support distinction is a little harder.
Report as:
Offensive Spam Harassment Incorrect Board