In the November election, you choose a slate of electors. Basically, each party nominates a slate of people (and their names normally do not appear on the ballot in most states) who are pledged to vote for that party's nominees for President and Vice President.
In most states, the ticket that gets the greatest number of votes statewide wins all of that state's electors. (Two states have a different set of rules by which they elect 2 electors statewide and 1 elector in each of the state's congressional district.)
In December, the people who were elected to serve as electors convene to cast the actual votes for President. Almost all of the time, they vote for the candidate to whom they were pledged. (In a typical election between 0 and 2 electors pledged to the losing candidate cast a protest vote for some other member of their party, but the remainde cast their votes as pledged.)