How is president of US elected?

America is a democracy. This means people vote for the president every four years. There are two main political parties (Republicans and Democrats), and several smaller parties (Libertarians, Green Party, and others). The parties put forward their candidates, all of whom campaign and try to win the public's support. Then, in early November, the people vote. There are two kinds of votes that are necessary in order to win -- the popular vote, and the electoral college.

Winning the popular vote (the majority of the votes cast by eligible voters) is not enough; one must also win enough electoral votes (currently 270 of them) in order to win the election. Each state that a candidate wins awards that candidate a certain number of electoral votes. The electoral college system was set up several hundred years ago, after the founding of the United States; and while it may have made sense 220 years ago, some people today find it confusing (in fact, there are often calls to eliminate it and go only by the popular vote). I enclose a link to an explanation of how electoral votes are decided.