In Catholicism and other Christian groups an altar can take one of two forms. Both serve the same function as the place upon which the Eucharist is confected or blessed.

Until very recently most Christian groups regularly practicing an established Eucharistic liturgy used altars designed so that the priest or minister would have his, in a few cases her, back towards the congregation. In Catholic and Orthodox circles the axis of the church is designed so that the priest at the altar can face East while celebrating the liturgy. While Orthodox communities are very consistent about eastern orientation of churches, Catholic churches frequently face in non-easterly directions. In the Catholic instance different interpretations are used to "make up" for the lack of physical eastern orientations for altars. Common is the idea that the priest and people face towards the figurative East of the coming Christ.

In the early 20th century many scholars called for the "turning around" of altars so that the priest or minister faces the congregation at all times during the liturgy. Catholicism rapidly switched to the versus populum position from the mid 1960s to the early 1970s. Conversion to the new posture of "facing the people", at least in the United States, is nearly universal in Catholicism and common in Lutheran and Episcopalian/Anglican communities. Orthodoxy has generally not warmed to non-eastern altar orientations. I only know of one "eastern" liturgy, the Maronite, that uses altars facing the people. These communities are in union with Rome, whose Latin Rite frequenly uses freestanding altars.

Much controversy surrounds the way an altar is situated in a church. Many like the prayerful, symbolic position of the priest/minister facing away from the congregation, a position that may add an element of mystery of the liturgy. Proponents of a fully visible liturgy contend that the congregation can only fully participate in the action of the liturgy when every action of the priest/minister is before them. Certain liturgies may only be practiced in the "eastern" orientation; in Catholicism, the Tridentine liturgy. It's interesting that an issue like altar orientation can cause so much passion between certain Christians.