When talking about artists?

What is meant in reference to "The Masters"? Someone e-mailed me saying "take what you learn from the masters and turn it into something new." But who are the masters...are they only the really famous artists from over 100 years ago, like da vinci and michaelangelo...do you include van gogh and monet? what about more recent claims to fame such as Andy Warhol and Jean-Michel Basquiat? Is there any artist still alive that we can refer to as a master? Perhaps, Jack Vetrianno? or Damien Hurst? What is everyones opinion on what makes a "Master" of the arts?