How does a presidential primary election differ from a general election?

A primary election is an election in which voters select candidates for a subsequent election. Primary elections are one means by which a political party nominates candidates for the next general election. Primaries are common in the United States, where their origins are traced to the progressive movement. There, primary elections are conducted by the government on behalf of the parties. Elsewhere in the world, the nomination of candidates is usually the responsibility of the political party organizations themselves and does not involve the general public.