There are two great mysteries in this world: the secret of the fox, and the purpose of the Dow Jones Industrial Average (DJINDICES:^DJI).

OK, so we figured out what the fox actually says ages ago, but have you ever stopped to consider what the Dow is meant to do? Spoiler alert: It's not designed to mirror the American stock market. The index is also not looking for the most attractive investment opportunities, or else ExxonMobil (NYSE:XOM) and AT&T (NYSE:T) might have been dropped from the Dow already.

In the video below, Fool analyst Anders Bylund mercifully avoids singing about the mysterious fox. Instead, he's explaining what the Dow really was designed to do and how astute investors can use it as a research resource.