Under the direction of Heavenly Father, Jesus Christ prepared this earth as a home for the children of God. God chose Adam and Eve to be the first people to live on the earth (see Moses 1:34; 4:26). Their mission was to bring mortality into the world and to be the first parents. (See Doctrine and Covenants 107:54-56.) When they chose to partake of the fruit of the tree of good and evil, they became mortal and were kicked out of the Garden of Eden.
When Adam and Eve left the Garden of Eden, they began to till the soil and perform other work to provide for their daily needs and the needs of their many sons and daughters. Soon the sons and daughters were marrying and having children of their own. In this way, they were providing bodies for Heavenly Father's spirit children. As the spirit children left Heavenly Father's presence, the memories of living with God left them - but they were not left alone. Heavenly Father sent the Holy Ghost to comfort, help and guide His children.
Adam and Eve prayed and taught their children to pray. Heavenly Father spoke to them and gave them commandments. They were obedient. An angel came to teach them about the plan of salvation, and the Holy Ghost came to testify of the Father and the Son and to teach them the gospel. (See Moses 5:4-9.) Our individual need for guidance from God is no different than that of Adam and Eve except in our circumstances. This is the reason why the Holy Ghost visits men, women and children today.
The Holy Ghost is a "personage of Spirit" (Doctrine and Covenants 130:22) and is a member of the Godhead. (See 1 John 5:7; Doctrine and Covenants 20:28.) He can be in only one place at a time, but His influence can be everywhere at the same time. The Godhead is composed of Heavenly Father, Jesus Christ, and the Holy Ghost. They are one in purpose although They each have an important assignment in the plan of salvation. Heavenly Father is our Father and Ruler. Jesus Christ is our Savior and Redeemer. The Holy Ghost is the Comforter as well as the revealer and testifier of all truth. The Holy Ghost is the messenger for our Heavenly Father and is a special gift from Him to us.
The mission of the Holy Ghost is to bear witness of Heavenly Father and Jesus Christ and of the truth of all things. We are promised, "By the power of the Holy Ghost ye may know the truth of all things" (Moroni 10:5).
The Savior taught, "And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent" (John 17:3). It is by the power of the Holy Ghost that we can know that Jesus is the Christ and that we can understand and live the gospel of Jesus Christ.
When the Holy Ghost bears testimony, He does it with such power that there can be no doubt that He is revealing truth. President Joseph Field Smith said, "When a man has the manifestation from the Holy Ghost, it leaves an indelible impression on his soul, one that is not easily erased. It is Spirit speaking to spirit, and it comes with convincing force. A manifestation of an angel, or even the Son of God himself, would impress the eye and mind, and eventually become dimmed, but the impressions of the Holy Ghost sink deeper into the soul and are more difficult to erase" (Answers to Gospel Questions, comp. Joseph Fielding Smith, Jr., 5 Vol. [1957-66], 2:151).
President Smith also said, "Through the Holy Ghost the truth is woven into the very fiber and sinews of the body so that it cannot be forgotten" (Doctrine of Salvation, comp. Bruce R. McConkie, 3 Vol. [1954-56], 1:48).
I have felt the presence of the Holy Ghost many times during my life. He has comforted me many times. He has revealed information and confirmed much knowledge. I know that He is real, and I am grateful each and every time He comes to me. Feeling the presence of the Holy Ghost is the best feeling!