Pluralism is the theory that many different groups run a country, rather than individuals. Pluralism critiques direct democracy and instead puts power in groups, such as unions, civil rights groups, lobbies and coalitions. This theory does not necessarily mean that all groups are equal or have the same amount of power.
Pluralism is especially relevant for the United States government, which has a decentralized government with many powers given to individual states, which then give powers to local governments to further decentralize power. Within each level of government there are also different branches that control different parts of the system so that no one person or group has too much power. Separation of power and the system of checks and balances is an essential part of both pluralist theory and the United States government.
In pluralism, the central government acts as a mediator rather than an all-powerful position that rules unchallenged. This fits well in the original creation of the United States, where the Founding Fathers wished to move away from the very centralized, elite government of England. Pluralism encourages competition between groups as they try to come up with the best way to deal with issues, so the society continues to move forward. Although there is value to theory, it is not an official system recognized by the United States government.