ILEEN - In Mosiah 15 it states that God, Christ and The Holy Ghost are one God. Please explain this scripture to me.

JOEL - Here are the scriptures in question:

1. AND now Abinadi said unto them: I would that ye should understand that God himself shall come down among the children of men, and shall redeem his people.
2. And because he dwelleth in flesh he shall be called the Son of God, and having subjected the flesh to the will of the Father, being the Father and the Son
3. The Father, because he was conceived by the power of God; and the Son, because of the flesh; thus becoming the Father and Son
4. And they are one God, yea, the very Eternal Father of heaven and of earth.
5. And thus the flesh becoming subject to the Spirit, or the Son to the Father, being one God, suffereth temptation, and yieldeth not to the temptation, but suffereth himself to be mocked, and scourged, and cast out, and disowned by his people. (Mosiah 15: 1-5)

Some critics refer to these scriptures claiming that Joseph Smith once believed in the traditional concept of the trinity, but Joseph once said:

"I have always declared God to be a distinct personage, Jesus Christ a separate and distinct personage from God the Father, and that the Holy Ghost was a distinct personage and a Spirit." (TPJS, p370)

First of all we need to understand how God, Christ and The Holy Ghost can be "one God" and at the same time be three separate individual Gods.
We worship only one God, and that one God is God the Father, Jesus Christ, and the Holy Ghost. They are separate and distinct beings and are individually called "Gods"(plural), but the three of them together are also called "God"(singular), being one in purpose and thought(John 17:11,21,22).
The word "God" can represent one being or all three beings; it depends on the context in which the word is used. It's kind of like a basketball team. People in Utah are fans of the basketball team called "Jazz". They are fans of each team member who is a "Jazz" and they are fans of the team as a whole which is also called "Jazz". So the word "God" can refer to one or all three beings of the Godhead.
We also need to understand that Jesus can be called "The Son" and "The Father" depending on the context. Heavenly Father is the Father of our spirits. Jesus is considered our "Father" also in three separate ways:
He is sometimes called "Father" because of his role as Creator. He is the Father of this earth.
He is also known as "Father" through the spiritual rebirth of mankind. When we are "born again" unto Christ we become known as the children of Christ, "his sons and daughters." He is the Father of our salvation (Mosiah 5:5-8; 15:10-13; 27:25-26; Alma 5:14).
He is also called Father because of his Eternal Parent investing him with power from on high and thereby alowing Him to represent our Heavenly Father.
Therefore, Heavenly Father is our Father and Jesus is also our Father.
In verse one above Abinadi is explaining how Christ will come to the earth to redeem His people. When he takes on a body of flesh and bone he physically becomes the Son of God. In verses 2 and 3 we learn that because He was conceived by the power of God, He can take on the title of "Father", because now that He has a body of flesh and bone, conceived of His Father, He can represent the Father. It also allows Him to take on the role as the Father of our salvation. In verse 4 we are told they are "one God" as I explained above, Heavenly Father being the God and Father of heaven and Jesus being the God and Father of the earth.