Light Of Christ

"The gift [baptism by fire] of the Holy Ghost, which members receive by laying on of hands, is very real and different than the spirit [light of Christ], which is given to all men, regardless of religious faith. This is known as the "Light of Christ" [conscience]. It is a light that when followed, will lead a man into the truth [Mormonism] of all things.
When that Truth [Mormonism] is received, and covenants made, then the Father, as taught in the Bible, will send the gift [baptism by fire] of the Holy Ghost, as a representative of the Son Himself. The gift [baptism by fire] of the Holy Ghosts' personal companionship, to an individual, is one of the greatest gifts that God can bestow on those, here upon the earth." (LDS Nana, Ask Mormon, Hubpages, brackets added, bold type added)

"The light of Christ [conscience] is a doctrine of the Latter Day Saint movement, including The Church of Jesus Christ of Latter-day Saints, that most people would call conscience. This doctrine teaches that the Holy Ghost itself is a divine personage and member of the Godhead. All people are able to feel the influence [spirit, light of Christ, conscience] of the Holy Ghost from time to time. But repeatedly going against the Light of Christ [conscience] will eventually make one "beyond feeling" the influence [spirit, light of Christ, conscience] of the Holy Ghost. The baptism of water spoken by Jesus to Nicodemus was a literal baptism as practiced in the church. The baptism by fire [gift] is to receive the Gift [baptism by fire] of the Holy Ghost, or the opportunity to always feel the Holy Ghosts' companionship, as long as one remains worthy of it." (www.statemaster.com/encyclopedia/Light_of_Christ, brackets added, bold type added)

Light of Christ does not appear in the Bible.

"Christ is" the true light that lighteth every man that cometh into the World." (D&C 93:2; John 1:9.) This enlightenment is administered to all men through the Spirit of Christ, or the Spirit of the Lord, or the Light of truth or the light of Christ [conscience] all of which expressions are synonymous. This spirit fills the immensity of space, is in all things, and is not to be confused with the Personage of Spirit as the Holy Ghost (or Spirit of the Lord.) (Doctrines of Salvation, vol. 1, pp. 38-54) The light of Christ [conscience] is the Spirit of the Lord which leads men to accept the gospel [Mormonism] and join the Church [LDS] so that they may receive the gift [baptism by fire] of the Holy Ghost... Men are born again [converted to Mormonism] by following the light of Christ [conscience] to the actual enjoyment of the gift [baptism by fire] of the Holy Ghost. (Mosiah 27:24-31; Alma 36.) It is because of the light of Christ [conscience] that all men know good from evil and enjoy the guidance of what is called conscience [light of Christ]. (Moro. 7:12-19.) It gives life to all things, is the law by which they are governed, and the power of God is manifest through it. (D&C 88:6-13.) (Mormon Doctrine, Bookcraft, Salt Lake City, Utah, Bruce R. McConkie, pp. 446-447)

"The phrase "Light of Christ" does not appear in the Bible, although the principles that apply to it are frequently mentioned therein. The precise phrase is found in Alma 28:14, Moro. 7:18, and D&C 88:7. Biblical phrases that are sometimes synonymous to the tern "Light of Christ" are "spirit of the Lord" and "light of life" (see, for example, John 1:4, John 8:18). The "spirit of the Lord," however, sometimes is used with reference to the Holy Ghost, and so must not be taken in every case as having reference to the light of Christ.
The light of Christ should not be confused with the personage of the Holy Ghost, for the light of Christ is not a personage at all. Its influence is preliminary to and preparatory to one's receiving the Holy Ghost. The light of Christ will lead the honest soul, who "hearkeneth to the voice" to find the true gospel [Mormonism] and the true church [LDS] and thereby receive the Holy Ghost (see D&C 84:46-48). (www.thefaithfuldissident.blogspot.com, bold type added, brackets added)

"Holy Ghost has no other effect than pure intelligence." (Teachings of the Prophet Joseph Smith, Joseph Fielding Smith, Deseret Book Company, p.149)

According to The Church of Jesus Christ of Latter-day Saints, Non-Mormons have: The Light of Christ ONLY, and Mormons have: The Holy Ghost or Holy Spirit by GIFT. To qualify for that GIFT of the Holy Ghost, you must by baptized into the Mormon church and receive the Holy Ghost by those who are in authority via laying on of hands.

"...the Holy Ghost enlightens their minds and enables them to know the truth [Mormonism] when they have faith in Christ and seek sincerely in order that they may accept and obey the truth [Mormonism]. However, there is no promise that the Holy Ghost will remain as a comforter and companion with even such as they [non-Mormons], except upon their acceptance of the truth [Mormonism] and their obedience to its requirements. (A Marvelous Work and a Wonder, LeGrand Richards, Deseret Book Company, 1978, p.119, bold type added, brackets added)

Mormonism teaches that it is the Holy Ghost who came on the Day of Pentecost, however, it was not the true Holy Ghost. It was merely the "Light of Christ." It states in the book, "A Marvelous Work and a Wonder" that the early apostles did not understand the scriptures, being without revelation, being without the priesthood of God, and they had to depend upon their own interpretation of the scriptures for their guidance. This book also states that they [meaning the early Christians] received the Holy Ghost [Light of Christ] to convince them of the truth as preached by Peter, nevertheless, they [meaning the early Christians] had not received the Holy Ghost as a gift [baptism by fire], in other words, laying on of hands by those in authority to receive such a gift.

Ask a Mormon about the Day of Pentecost, most likely, he/she will not fully know much about it.