Do US citizens vote directly for President?

No, actually they don't. During a presidential election, citizens vote for a member of a electoral college to cast their vote for them. States are given a number of votes based on the population of the state. For each vote a state has, a member of the electoral college is assigned to reflect the results of the people's vote.

The scary thing is, the member of the electoral college does not necessarily have to vote in the light of the people. This system was put in place to prevent the people from voting in a dangerous tyrant into office! Although, in all of U.S. history, this has not happened...yet...