Mixologist or Bartender?

So we are starting to see more titles of that person who makes your drinks or serves you a beer as a mixologist.  Where did it come from?  What is the difference of that person who we call a bartender and those who refer to themselves as mixologists?

Here’s an article that breaks it down…

http://www.nightclub.com/blog/the-scene/news/bartenders-vs-mixologists-whats-difference