Democratic presidential candidate Hillary Clinton speaks about the results of the South Carolina primary to supporters at a primary night party in Columbia, South Carolina, Feb. 27, 2016. Reuters

More Americans voted for Democrats Hillary Clinton this year for president over Republican Donald Trump. But she won't be president in 2017 and he will.

That's because presidential elections in the United States are decided by the Electoral College, not voters. The nation's founders set up the system to ensure that states had an equal say in who was elected president, regardless of the population in each state. That means voters who live in states with fewer people have somewhat of an outsized say in who in gets be president, a system that has for decades favored Republicans, who tend to appeal to rural voters more than Democrats do in part because Democrats favor progressive policies such as abortion rights and gay marriage that don't go over well with conservative, Christian voters in small towns. Democrat Al Gore also won the popular vote in 2000, but he lost the White House to Republican George W. Bush, who won the Electoral College vote.

Remember those party insiders many voters seemed to rail against all year by backing Trump and Democrat Bernie Sanders in the primaries? They get to choose the next president. There are 538 electors from all 50 states and the District of Columbia who decide the Electoral College vote. That figure represents the number of congressional seats the state has in the House and Senate. The voters tend to be state party officials chosen at the party's state conventions. All of a state’s electoral votes go to the candidate who won the most votes. The candidate who receives at least 270 Electoral College votes becomes the next president.

Clinton picked up densely populated and diverse states such as California, New York and Illinois, winning 104 votes just from those states under the Electoral College system. In all, she won nearly 61 million votes, and could reach the 66 million votes Obama received in 2012 by the time all the votes have been counted in California and New York.

But Trump picked up large and diverse states such as Texas and Florida, and he also won a handful of swing states that backed President Barack Obama in 2012, making him the clear winner under the Electoral College system. He already met with Obama this week to discuss his transition to the White House, even as Clinton voters across the nation held protests against his victory.

So when is this all going down? The Electoral College picks the next president on the first Monday after the second Wednesday in December. This year, that falls on Dec. 19.