What is an elector and who chooses him or her?
The names of the electors on which the public votes are submitted by the political parties to the states before each presidential election. Whichever party wins each state will have its slate of electors comprise the Electoral College of that state.

For example, Virginia has two senators and eleven representatives for 13 Electoral College votes. All political parties will submit a list of 13 names to the state of Virginia before Election Day in case they win the popular vote. The names on the list of the victorious party will become the electors from the state of Virginia.

Why do we have an Electoral College?  Who came up with the system and what is the basic idea behind it?
It is the result of a hard-fought compromise reached by the framers of the Constitution during the Constitutional Convention of 1787. The framers debated many options for choosing the nation’s highest office. Some wanted popular elections, while others wanted Congress to make the choice without public input. The compromise they made falls somewhere between these two options. In his Federalist Papers, Alexander Hamilton summed up how he and many of the framers may have felt about the system, noting “that if the manner of it be not perfect, it is at least excellent.”

Is there a connection between the Electoral College and the popular vote?
Yes and No. In all states (except two), the winner of the popular vote in that state wins all of the electoral votes in that state. However, the winner of the Electoral College vote is not necessarily the winner of the national popular vote. Your vote matters at the state-level.

Which states use a “winner-take-all” system for counting electoral votes?
48 States and the District of Columbia use a winner-take-all system. Nebraska and Maine do not.

Does the number of electors a state has ever change?
Yes. The number of representatives in each state may change after the decennial census. Since the number of electors is based on the number of representatives and senators, any change in the number of Representatives affects the number of votes for that state in the Electoral College.

What the Electoral College's timeline? 
November 4 – Popular Election
December 15 – The electors meet in each of the States to cast votes for President and Vice President.
January 8 – Congress counts the votes
January 20 – Inauguration Day

During which elections has the Electoral College vote been different from the popular vote?
1876, 1888, and 2000

What happens if the candidate who wins on Election Day dies or resigns before Inauguration Day?
One possible scenario is if the candidate dies or resigns in between the popular vote and the Electoral College vote. Both major political parties have rules that allow them to replace their candidates on the ballot after the party convention. If, for example, Republican X won a majority of pledged electoral votes on Election Day but died the week before the Electoral College met, the Republican Party would tell the electors pledged to Republican X to vote for replacement Republican Y. (There is no legal problem with this replacement, but the party is unable to force its pledged electors to vote a certain way. Whether or not the electors would follow the national party’s instructions is unclear.)

The most difficult scenario occurs should the winning candidate die or resign between the meeting of the Electoral College in mid-December and the counting of the electoral votes by Congress on January 6. If the Democratic Candidate X received a majority of the Electoral College votes when the electors met in mid-December, but dies before the Congress officially counts the votes from the states, Congress has two options:

The first option is to count all of the votes as received from the states. In our example, Democratic Candidate X received a majority of the votes and would be declared the president-elect of the United States. On Inauguration Day, the provisions of the Presidential Succession Act of 1947 would go into effect and the vice president-elect would become the president of the United States. The second option is for Congress to invalidate all of the electoral votes for the deceased candidate. In this instance, there is likely to be a vice president-elect but no candidate with a majority of votes for presidency. The presidential contest would be decided by the House of Representatives where the state delegations would only be able to consider the other candidate(s) receiving electoral votes. 

The final scenario is if the president-elect dies or resigns after the electoral vote is counted by Congress but before Inauguration Day. The Presidential Succession Act of 1947 would go into effect on Inauguration Day.