The election of President and Vice President of the United States is an indirect election in which citizens of the United States who are registered to vote in one of the 50 U.S. states or Washington, D.C. cast ballots for members of the U.S. Electoral College, known as electors. These electors then in turn cast direct votes, known as electoral votes, for President and Vice President. The candidate who receives an absolute majority of electoral votes for President or Vice President (currently, at least 1 out of a total of 538) is then elected to that office. If no candidate receives an absolute majority for President, the House of Representatives chooses the President; if no one receives a majority for Vice President, then the Senate chooses the Vice President.

Presidential elections occur quadrennially with registered voters casting their ballots on Election Day, which since 1845 has been the first Tuesday after November 1. This date coincides with the general elections of various other federal, state, and local races; since local governments are responsible for managing elections, these races typically all appear on one ballot.

More Info: en.wikipedia.org