The Content of Christian Worship

It is not possible to give a complete description of Christian worship. Congregations worship in quite different ways. Worship services vary from formal services with wonderful classical music and well-planned liturgical actions, to a small group gathering around a table and using an impromptu service with rock music.
Worship tends to have two major centers: the Word and the Sacraments. The Protestant tradition tends to emphasize the proclamation of the Word. This includes readings from the Bible, and a sermon, which will normally help the congregation understand the reading and apply it to them. Historically, the sermon was a major means of conducting adult Christian education, and of spurring both individuals and congregations to make necessary changes. Protestant worshippers had a surprising appetite for sermons: three-hour sermons were not uncommon. (This appetite does not seem to have survived into the 20th Century.)
Of course Catholic worship also includes readings from the Bible and some exposition. This is normally referred to as a "homily", rather than a sermon. However the center of worship in the Catholic church, as well as other "liturgical" churches, is the sacrament of Communion, which will be discussed below. For them it is normally celebrated at every regular service. The elaboration and formality tends to be greater than it is in Protestant churches. Protestants normally celebrate communion either 4 times a year or once a month.
In addition to the Word and sacraments, services of all groups include prayers and singing. One analysis of the prayers classifies them according to the acronym ACTS: Adoration, Confession, Thanksgiving, and Supplication. Another variant is ACTIS, with the I standing for Intercession.
Services often begin with a combination of prayer, responsive readings and music which simply celebrate being in God's presence. This is adoration.
Fairly early in the service there is normally a prayer of confession. In confession we express both our individual faults and those of the community. We ask God to help us to amend them, and receive assurance (normally in words taken from the Bible) of God's willingness to do so.
Thanksgiving acknowledges God's goodness to us. Thanksgiving is important in the Christian life. As we thank God for things, we put those things into the context of our relationship with God.
In Supplication we ask God for what we need. In worship, this supplication normally includes the needs of the congregation, nation, and world. Intercession is a specific kind of request, directed towards the needs of others. Intercession is particularly important to Christian life, because it is one of the key elements in the pattern of "exchange" that I referred to in a previous article. Through intercession we bear each other's burderns, and join the other members of the community in putting their requests before God.