Per the National Archives and Records Administration (NARA) website, Archives.gov - it is a PROCESS
A majority of 270 electoral votes is required to elect a President. There are 538 "electors" (each state's allocation is the number of members of its Congressional delegation (i.e., 1 for each House member , plus 2 for Senators).
Who are these electors, and how are they chosen? "The political parties in each state choose slates of potential Electors sometime before the general election. Second, on Election Day, the voters in each state select their state's Electors by casting their ballots for President.... Generally, the parties either nominate slates of potential Electors at their state party conventions or they chose them by a vote of the party's central committee
Political parties often choose Electors for the slate to recognize their service and dedication to that political party. They may be state elected officials, state party leaders, or people in the state who have a personal or political affiliation with their party's Presidential candidate." NOTE: No Senator or U.S. Representative can be an elector (Article II, Section 1)
Electors meet in their respective states on : " the first Monday after the second Wednesday in December after the presidential election" - Dec. 19, 2016
Each state's electoral votes are counted : "in a joint session of Congress on the 6th of January in the year following the meeting of the electors" - As President of the Senate, the Vice President presides, and announces the results of this vote
"Most states have a “winner-take-all” system that awards all electors to the winning presidential candidate. However, Maine and Nebraska each have a variation of “proportional representation"