Within the Christian religion are two branches: Roman Catholicism and Protestantism.

Roman Catholics recognize the pope as the head of the church and the ultimate authority on faith and morals. The pope is elected by cardinals who also serve as an advisory council to the pope. In addition, the pope is advised on church matters by a synod of bishops and on church government by the Curia Romana (the secretariat of state and various congregations, councils, tribunals, and offices that handle church administration). Most of the world is organized into dioceses, or sees, each headed by a bishop. Dioceses are grouped into church provinces, or archdioceses, each under an archbishop. Dioceses are divided into parishes, each served by at least one priest. Priests, addressed as "father," are ordained ministers empowered to celebrate Mass and administer the sacraments. Unordained members of religious orders are addressed as "brother" or "sister." Deacons perform the duties of priests except for celebration of Mass and administration of the sacrament of penance and reconciliation.

The Protestant branch of Christianity has several denominational families, the major ones being the Lutheran churches, Anabaptist groups (Amish, Mennonite, and Hutterian Brethren), the Anglican or Episcopalian church, Calvinist churches (Presbyterian and Reformed), Congregational churches (Independent, United Church of Christ), Baptist churches, Methodist churches, and Revivalist groups (Adventists, Pentecostals, and Disciples of Christ). Each of these families has several divisions, or religious bodies, which differ slightly in certain doctrines and practices. For example, the Southern Baptist Convention and the National Baptist Convention USA Inc. are separate bodies of the Baptist denominational family. The Evangelical Lutheran Church, the Lutheran Church-Missouri Synod, and the Wisconsin Evangelical Lutheran Synod are bodies that belong to the Lutheran denominational family.

In most Protestant denominations, the congregation is the unit of church organization and the source of authority. Denominational bodies may act as advisory bodies or have a considerable amount of authority over congregations. Most congregations have at least one minister, sometimes called a preacher or pastor, who is usually ordained, and presides over religious services, delivers sermons, and leads liturgies and ceremonies. Ministers also take care the congregation's needs, including education, counseling, visiting the sick and dying, and social and community outreach. Many ministers are involved in evangelical work, or preaching their beliefs to others outside the congregation. Ministers may be assisted by other ministers, elders, deacons, music directors, school teachers, financial managers, and others, depending on the size of the congregation.

The Jewish religion in the United States has four movements: Orthodox, Conservative, Reform, and Reconstructionist. Each movement has a central organization, and synagogues, or temples, are often affiliated with these organizations, but synagogues are usually independent community organizations.

The spiritual leader of a Jewish congregation is the rabbi—a title taken from the Hebrew word meaning "master"—who is an authority and teacher of Jewish law. A rabbi can perform rituals and conduct services, but has no more authority to do so than any other adult male member of the Jewish community. In fact a synagogue can operate without a rabbi and have services led by lay people. Rabbis decide questions of Jewish law and ritual. They are teachers who instruct the congregation and resolve disputes about Jewish law.

Smaller synagogues may have only one rabbi while larger synagogues may have a chief rabbi and one or more assistant rabbis. Most congregations also have a cantor, or hazzan, who leads liturgies and prayers. Cantors are trained in both music and religious education. Both rabbis and professional cantors are ordained clergy and both have the authority to conduct weddings, funerals, visit sick synagogue members, and teach adult education classes.

The religion of Islam has two branches. The majority of Muslims are Sunnites and are orthodox. The Shiites broke away from the Sunnites because of differences in beliefs about the rulers of Islam, called imams. The Shiites are divided in a number of groups, including the Imami, the Zaidis, and the Ismailis.

Muslims say prayers privately in their homes or at a mosque. A weekly worship service is held on Fridays, which includes the ritual prayers, a reading from the Koran, and a sermon. Islam has no universal leader and no ordained clergy or priesthood. Religious teachers, called ulemas, or mullahs, supervise mosques, religious and theological education, handle legal cases in court regarding Islamic law, and preach Islam, among other responsibilities.

Hinduism has about 200 sects that seem to be separate religions, but they all come from common traditions. Beliefs range from primitive forms of animism to the highest reaches of mysticism and philosophy. Most sects have a mystic strain and all stress nonviolence.

Hindu worship for the most part takes place in the home. A Hindu temple or shrine is considered an abode of a deity and is not used for communal worship. There are many kinds of Hindu clergy. Temple priests collect offerings and care for temples and shrines. Domestic priests perform rites involving births, marriages, and deaths. Gurus are spiritual teachers. Sadhus are monks; most live in monasteries, but many live as wandering mendicants (beggars).

Buddhism has two major divisions: Theravada Buddhism and Mahayana Buddhism. There are numerous sects with varying practices and beliefs. Theravada Buddhism is an austere religion that requires solitude, meditation, and self-mastery through which each member hopes to achieve nirvana. Many of its followers are monks and nuns who spend most of their time in meditation and teaching. Mahayana Buddhism is less austere and emphasizes liberation for everyone through good faith and good works. Mahayanans have elaborate temples presided over by priests. They have colorful festivals and solemn rituals. The many Mahayana sects include Zen, Jodo, Shin, Tendai, and Nichiren Shoshu. Some sects, such as Zen, have monks and maintain monasteries. In the United States, there is no national Buddhist organization. Some groups have ties to organizations in Asia and some have networks of affiliated communities in this country, but for the most part, American Buddhism is divided into many different groups and factions, each with its own organizational structure, teachings, and practices.

Although only the major religions in the United States are discussed here, many of the smaller religions are patterned after the larger ones in how they are organized and run.

Most have some type of building, such as a church or temple, or simply a designated meeting place for adherents to gather and worship, pray, hold rituals, and teach according to their belief system. Most religions have clergy or leaders who guide, teach, and organize adherents, and who are knowledgeable in the religion's laws, writings, chants, prayers, and songs.

Some congregations have full- and part-time paid positions, particularly for clergy. Most congregations have a combination of paid and nonpaid positions. Larger congregations that are affiliated with major religious groups can pool resources and afford to hire officials. Some religions and congregations provide room and board for officials and pay them a small stipend for living expenses. Paid workers in congregations can include clerical/administrative workers, building and ground managers, musicians, librarians, and teachers at all levels, kindergarten through high school. Some churches, temples, and mosques have schools associated with them to provide both general and religious instruction to children of all ages. Most of the major religions also have colleges and seminaries where their ordained clergy are trained.

Smaller religious groups may have very little or no funding. Officials may volunteer or be elected by adherents. The adherents volunteer their time, talents, and financial resources to support the congregation.