The sacrament is what the movement calls what other Christians call communion or the Eucharist, and it is the reason the meeting exists. Latter-day Saints do not regard the bread and water as changed in substance, and do not use the language of sacrifice; the ordinance is understood as a renewal of the covenants made at baptism, and as a weekly act of remembrance.
The mechanics are performed almost entirely by teenagers. Young men of sixteen and older, ordained priests in the Aaronic priesthood, break the bread and then kneel to read the two sacramental prayers. Those prayers are fixed word for word, given in section 20 of the Doctrine and Covenants, and if a word is misread the young man is asked to begin again, which is one of the very few points of exactness in an otherwise informal service. Deacons, boys of twelve and thirteen, then carry trays of bread and small cups of water along the rows. Everyone present may partake. Children take it, visitors take it, and no announcement restricts who may.
Water replaced wine over the later nineteenth century as the Word of Wisdom came to be enforced more strictly, on the warrant of an 1830 revelation stating that it mattered little what was used so long as it was done with an eye single to the glory of God.
On the first Sunday of most months the assigned talks are set aside and the microphone is opened to anyone in the congregation who wishes to speak.