So, basically, The Book of Mormon is ancient scripture that you can compare with the Bible. Like the Bible it is the words of prophets who testify of Jesus Christ and that he is our savior.
It begins at about 600BC (at around about the time of Jeremiah in the Bible). In it God commands a prophet called Lehi to take his family out of Jerusalem. They leave and are guided to the sea, where his son Nephi constructs a ship. They travel across the sea to the American continent where they begin to establish a civilization.
They split off into two groups when they got there. One group called Nephites followed Nephi. The other group followed his older brother Laman, and called themselves Lamanites. These two groups fought against each other.During this time God chose many prophets within these groups and they taught the gospel to the people and that the savior of world would visit these people. This is the main event in the book of Mormon. (This happens in 3 Nephi chapter 11 Page 427). Jesus actually talks of this to his disciples but they do not understand what this means, John 10:16 "And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd."
Here he was talking of visiting his other followers.
After Christ visited these people they lived in peace for a long time. Slowly there began to be disagreements between them again and they ended up splitting back into two groups. They began to war with each other again. During this time a prophet called Mormon gathered the records and prophecies together and compiled them into one book and inscribed them onto Gold Plates, and this is why it is called The Book of Mormon. He then passed the plates to his Son Moroni, who added a little bit to the record and then buried it in the ground.
So that is how it was written, but how did we come to get this? Well, in 1823 Joseph Smith was visited by Moroni, now an Angel, who instructed Joseph where to find the plates. Joseph then found them. After 3 years he took the plates from the ground. He then translated it, using the means God gave him to translate them. It took him only about 65 working days to translate the entire book, and is just one of the fruits that came from God calling him as a prophet.
The best thing about what we teach though is that you do not have to take our word for it. We encourage everyone to read The Book of Mormon for themselves, ponder in there hearts the message it contains and then ask God, the Eternal Father, in the name of Jesus Christ if these things are true. And those who do this will receive an answer through the Holy Ghost that it is the word of God. This promise is given in The Book of Mormon (Moroni Chapter 10 Verse 3-5, on page 529).
