The Electoral College was included in Article II, Section 1, Clause 2 of the US Constitution to Elect the US President. There is also a Popular Vote but the Electoral College vote determines who will be the President. The Electoral College is comprised of the same number of Electors as currently exist in the US House of Representatives for each State, plus 2 Electors for each State. In 2020 the Electoral College had 538 Electors, with 270 votes required to Win the US Presidency (an absolute majority). If no one achieves an absolute majority, the President will be elected by the US House of Representatives and the Vice President will be elected by the US Senate.
Who is selected to be an Elector at the Electoral College is determined by each State’s Legislature (Federal Office Holders Cannot be Electors). The rules for Voting as an Elector vary by State. Currently, most Electors vote for the Candidate who won the most State Districts in their States (“winner take all”). On this basis, a candidate may be elected as President who did not win the overall popular vote.
The Electoral College Meets in December and the new US President is inaugurated in January.