When Christians talk about worship they are referring to the practice of putting God first in their lives. This can be done either in private worship or in public worship - for example, Sunday church service. Christians worship personally, privately, and collectively. Some denominations use rituals, sacred objects, symbolism, and liturgy. Other denominations are non-liturgical and take a different approach in their worship. There are various expressions of worship that can include music, dance, prayer, study, art, and serving others. The central ceremony in most Christian denominations is the Eucharist or Holy Communion. Holy Communion is a ritual instituted by Jesus in which bread and wine are prayed over and then consumed by the faithful in memory of Christ. The holy meal is considered to be a sacrament in most Christian churches. Despite Holy Communion being a common practice among most Christian groups, some denominations contest what the bread and wine represent and how the ritual of Communion should be practiced due to Scripture’s ambiguity as to those specifics. Beliefs diverge as to the nature of the Communion bread and wine, the frequency with which believers should receive Communion, who should serve Communion, who should receive Communion, what prayers should be said during Communion.