[quote="ParkerD, post:5, topic:232382"]
I suppose that I'll give a fairly brief explanation about the LDS view (from my perspective) of "what is the atonement of Christ, and what did it achieve," although it certainly won't be exhaustive (meaning cover the full scope of the subject). One desiring to study this topic in depth can easily do an lds.org search on the topic and find many articles, plus book references such as James E Talmage's Jesus the Christ, John Taylor's Mediation and Atonement, and other books that are more recent.
I like using the primary scriptural sources, and although the Book of Mormon and the Pearl of Great Price give greater clarity about this subject on certain points, the major doctrinal points are readily found in the Bible and those will be the sources for this brief explanation:
1) Jesus Christ, the Only Begotten Son of God the Father, is the "Lamb slain from the foundation of the world." (Revelation 13:8) Thus, His atoning sacrifice was fore-planned, foreordained, and He voluntarily offered Himself as that great and last sacrifice (which was to be completed on this earth during His life on earth as Immanuel and the Promised Messiah) for the sins of the world. He offered Himself during a council meeting in Heaven, which was followed by a War in Heaven wherein Satan rebelled against the plan of God and the voluntary offering of Jesus Christ. (See Revelation 12:7)
2) He is the "lamb without blemish" (see Exodus 12:5), meaning that He had no personal sins and also was God in the flesh and thus could indeed be the great and last sacrifice without the need for any pre-cursor offering to cleanse the officiator (priest) such as occurred under the law of Moses with animal sacrifice.
3) He "hath borne our griefs, and carried our sorrows" (Isaiah 53:4) in such a personal way that He knows all of those intimately and can indeed succor us in our hour of need because He suffered those exact pains, sicknesses, sorrows, griefs and turmoils. This is why He can "bind up the brokenhearted", "comfort all that mourn", and "give unto them beauty for ashes, the oil of joy for mourning, the garment of praise for the spirit of heaviness;" (Isaiah 61:2, 3) it is also why in the resurrection we will have perfect bodies through the grace of His great and last sacrifice.
4) "He was wounded for our transgressions, He was bruised for our iniquities: the chastisement of our peace was upon Him; and with His stripes we are healed." (Isaiah 53:5) He makes intercession for us, the transgressors. (v. 12) He and the law of justice and mercy require that we "make His soul an offering for sin" (v. 10) in order for His atoning sacrifice to be fully efficacious for us.
5) He desires to offer unto us the "sure mercies of David" through our completing an "everlasting covenant" which He offers to make with each of us. (Isaiah 55:3)
6) The "key of the house of David" is laid "upon His shoulder"; "so He shall open, and none shall shut; and He shall shut, and none shall open." (Isaiah 22:22) He was fastened as a "nail in a sure place". (v. 23)
7) His atonement began in Gethsemane when He prayed while great drops of blood came from every pore, continued during the false trial and the agony of His crucifixion, and was completed with His resurrection when He became the first fruits of them that slept and showed that our resurrection will be possible through His atonement and resurrection.
(To be completed later)
8) The agony of His pains during that period of completion of His atoning sacrifice were infinitely greater than any mortal person could have endured. Only He, the Son of God who was Immanuel, could have endured those pains and lived through it.
9) He voluntarily gave His life and died, giving up the ghost, from whence His spirit went to the spirit world where He "proclaim[ed] liberty to the captives, and the opening of the prison to them that are bound" (Isaiah 61:1) and "preached unto the spirits in prison;" (1 Peter 3:19) so that they could be "judged according to men in the flesh, but live according to God in the spirit." (1 Peter 4:6)
They will be judged according to the promise that "unto [Him] every knee shall bow, and every tongue shall swear." "In the Lord shall all the seed of Israel be justified, and shall glory." (Isaiah 45:23, 24)
10) His earnest desire is that "all mine are thine, and thine are mine; and I am glorified in them." (John 17:10) Also, "That they may be one; as thou, Father, art in me, and I in thee, that they also may be one in us:...And the glory which thou gavest me I have given them; that they may be one, even as we are one:...that they may be made perfect in one;...that the love wherewith thou hast loved me may be in them, and I in them." (See John 17:21-26)
11) His atonement and offer to bring us to God through His redeeming blood of reconciliation apply to all mankind, old and young, bond and free, of all nationalities and regardless of their religion through each person's free will choice, so long as they are willing to allow Him to Shepherd them through their covenants made and covenants kept, and willingly accept His gospel whereby He can enable the full efficacy of the plan of salvation in their behalf. Those who died before an age of personal accountability are reconciled to God through His redeeming blood through their own personal innocence from sin and through His atoning grace.