When Jesus Christ was on the earth, he had authority from his Father to do what he did.
He had the priesthood and the authority to act in God's behalf and in his name.
After Christ and the apostles and early priesthood leaders were killed, the priesthood was lost to the earth.
So where did all the churches since then get their authority? They decided on their own to create religions based on their desires to follow God. They used their own authority to act in God's name. Some tried to follow the truth, but little by little, the teachings of men replaced Christ's true gospel.
No church had the priesthood. That's right, not one.
We Mormon's believe that the authority was lost and the only way for it to be back on the earth was if God restored it. That is exactly what we believe happened in the early 1800's.
When he was 14, Joseph Smith wanted to know which church to join. It was confusing because every church insisted they had the truth and everyone else was going to hell.
What did he do? He looked in the bible for an answer. He read, "if any of you lack wisdom, let him ask of God..."
He believed in the bible and God's teachings. He went to a grove of trees to pray. As an answer to his prayer, God and his son Jesus Christ appeared to him.
They told Joseph that he should join none of the churches because they taught the philosophies of men mingled with scripture. He was told that the truth was no longer on the earth and that there was no one that had God's priesthood authority.
Joseph was told that God would restore the truth and the gospel to the earth. It would be restored through Joseph. It would have the priesthood authority to administer the gospel and the ordinances that had been lost from the earth.
The truth has been restored. Priesthood authority to baptize has been restored.
The organization set up by Christ has been restored with a living prophet and twelve apostles who guide his Church today.
His Church is The Church of Jesus Christ of Latter-day Saints.
It is true.