As above this is served by well dressed young men who hold a level of Mormon Priesthood. This in itself is a good Christian principle. Again like Christian Churches this is done in remembrance of what Jesus did for us.
LDS.org says this about the Sacrament:
On the night before His Crucifixion, Jesus Christ met with His Apostles and instituted the sacrament (see Luke 22:19–20). After His Resurrection, He instituted the sacrament among the Nephites (see 3 Nephi 18:1–11). Today the sacrament is an ordinance in which Church members partake of bread and water in remembrance of Jesus Christ’s atoning sacrifice. This ordinance is an essential part of worship and spiritual development. Through this ordinance, Church members renew the covenants they made with God when they were baptized
Under additional information it also says this:
Partaking of the sacrament is a witness to God that the remembrance of His Son will extend beyond the short time of that sacred ordinance. Part of this ordinance is a promise to remember Him always and a witness of individual willingness to take upon oneself the name of Jesus Christ and to keep His commandments. In partaking of the sacrament and making these commitments, Church members renew the covenant they made at baptism (see Mosiah 18:8–10; D&C 20:37).
This paragraph touches on where I am going with this, the idea that not only is the Sacrament a remembrance of Christ but its a weekly renewal of the covenant made at baptism. What is that covenant?
Those who are baptized enter into a covenant with God to take upon themselves the name of Jesus Christ, keep His commandments, and serve Him to the end (see Mosiah 18:8–10; D&C 20:37). Church members renew this covenant each time they partake of the sacrament (see D&C 20:77, 79).
Those who keep the covenants they made at baptism are blessed by the Lord for their faithfulness. Some of the blessings include the constant companionship of the Holy Ghost, the remission of sins, and the privilege of being spiritually reborn. If they continue faithfully, they are promised eternal life (see 2 Nephi 31:19–20).
So at baptism, this says LDS members are taking on the name of Jesus Christ covenanting to keep the commandments, and are spiritually reborn, if they continue faithfully, so then the sacrament is a weekly renewal of this covenant.
So what does this mean? To Christians the idea of coming to God and humbly saying I have messed up lately and I just want to recommit myself to You is nothing new. However for us when you are born again and when you have recieved justification, meaning righteousness in the sight of God this is a one time event.
Romans 4:5 But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness.
Which results in this
2 Corinthians 5:17 Therefore, if anyone is in Christ, the new creation has come: The old has gone, the new is here!
Galatians 2:20 I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me.
So if you are a Christians with faith in Christ, He now lives in you and you are saved from the consequences of your sin as a result of this new covenant of grace. So is the LDS church living in this same covenant?
2nd Mormon President Brigham young regarding the sacrament said:
“Its observance is as necessary to our salvation as any other of the ordinances and commandments that have been instituted in order that the people may be sanctified, that Jesus may bless them and give unto them his spirit, and guide and direct them that they may secure unto themselves life eternal.” (Discourses of Brigham Young, p. 266).
This next more recent quote captures my point fully.
“The scriptures repeatedly teach that the Spirit of the Lord will not dwell in an unclean tabernacle. When we worthily partake of the sacrament, we are promised that we will ‘always have his Spirit to be with [us].’ To qualify for that promise we covenant that we will ‘always remember him’ (D&C 20:77). (Dallin H. Oaks, “Pornography,” Ensign (Conference Edition), May 2005, p. 88. Brackets in original).
A question from the Apostle Paul comes to mind:
Galatians 3:2 This only would I learn of you, Received ye the Spirit by the works of the law, or by the hearing of faith?
What do you think his answer was?
So what the sacrament is, is a weekly reminder of the needs of LDS members to live in a manner that is worthy and renew their covenant in this maner of living and thus renew the presence of the Holy Ghost in their lives, without this renewal the Spirit would cease to dwell with them and ultimately their whole basis for staying worthy and current in the Mormon gospel would cease.
In the Book of Mormon, Mormon 9:29 it says:
“See that ye are not baptized unworthily; see that ye partake not of the sacrament of Christ unworthily; but see that ye do all things in worthiness, and do it in the name of Jesus Christ, the Son of the living God; and if ye do this, and endure to the end, ye will in nowise be cast out”
You must stay worthy to take the sacament and you also must take the sacrament not to be cast out.
So why is this such a problem, well our covenant is between us and Christ and it is a forever covenant that once in place, stays in place, Romans 8:1 says there is no condemnation for those that are in Christ, its a legal agreement between you and God that once you are in Christ you are free from the consequence of sin and this is not something that regularly needs to be topped up by having water and bread.
What about being worthy to take the sacrament, think about who was there in the last supper when Jesus passed around the bread and wine.
Who is it, well its Judas, early in the book of John what did Jesus say about Judas?
John 6:64 But there are some of you that believe not. For Jesus knew from the beginning who they were that believed not, and who should betray him.
John 6:70 Jesus answered them, Have not I chosen you twelve, and one of you is a devil?
Yet despite this Judas is there in the last supper, taking the sacrament as the LDS would say. Why would Jesus allow someone so unworthy to take it?
The answer is that taking this bread and wine is not a covenant renewal between a person and God that must only be taken by someone who is worthy but it is as Jesus said:
1 Corinthians 11:24-2524And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me.
25After the same manner also he took the cup, when he had supped, saying, this cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me.
Its this simple, we take bread and wine, or water, or juice, in remembrance of Him, its that simple, anyone can do it that loves Him and wants to remember and honour Him.
This idea of this “Sacrament” as being a requirement in order to retain the Holy Ghosts presence is a man made requirement similar to that of the Pharisees, taking Gods ways and making them harder on people than God ever wanted.