The Electoral College: it's a phrase you hear every four years, but what *is* it? Simply put, it's the system the U.S. uses to elect its president. Instead of directly voting for a candidate, citizens vote for a slate of 'electors' who pledge to support that candidate.
Each state gets a number of electors equal to its total number of representatives in Congress (House + Senate). These electors then cast the actual votes for president. In most states, the candidate who wins the popular vote receives all of that state's electoral votes – a 'winner-take-all' system.
Why do we have it? The Founding Fathers created it as a compromise between a popular vote election and a Congressional election of the president. While it aims to balance the power of populous and less-populous states, it's often a source of debate, especially when the popular vote winner doesn't win the presidency. Understanding the Electoral College is key to understanding American elections.