We have two major parties, and several smaller ones- the Libertarian Party and the Green Party are the two largest third parties generally. However, there are also sub factions within the major political parties, so that they in fact makeup a sort of coalition of sub factions, similar to the coalitions of parties you see in other countries. This means that primaries are a super important part of the election cycle in the USA. The Primaries are like the first round of a two round system.