That distinct flavor of sourdough bread is due to the lactic and acetic acid that bacteria growing in the sourdough culture produce. Interested in learning more? Read me!
Essentially you mix together equal parts flour and water and since there is yeast on the flour and in the air a culture grows! As long as you "feed" the culture every 8-24 hours you're golden.
I'm following this video (the guy is pretty goofy...):
I'm a little nervous because I'm using whole wheat flour from Earnst Farms and the dude is using white flour. I'm wondering if that will screw up the flour to water ratio? I guess we'll see!
Sourdough Starter Day #1
Here's a pretty interesting article on the health benefits of sourdough bread.