In response to Nephi's pondering on his father's vision, he was caught away in vision onto a mountaintop. The Spirit of the Lord questioned him about his belief in his father's vision, commended for his belief in the Son of the Most High God, asked what he wanted, and then showed it to him. One of the interesting comments of this vision is that the Spirit of the Lord appeared to Nephi in the form of a man.
An angel then descended to give Nephi a guided tour in which he saw a virgin, who is identified as the "mother of the Son of God, after the manner of the flesh". There are some who have made a great deal of this particular phrase and what it might mean about how Jesus might have been concieved, but all of it is speculative. Nephi was not shown details: The woman was carried away in the Spirit, and then reappeared holding a child.
Nephi was then given a preview of Jesus' ministry, including his baptism at the hands of the prophet his father had spoken of, his receiving the Holy Ghost, his miracles and healings, twelve disciples, called the apostles, and his trial and crucifixion. In the course of the vision, several of the symbols of Lehi's dream were interpreted: the Iron rod being the word of God, the tree and a fountain of living water being the love of God, and the great and spacious building without a foundation being the pride of the world. Nephi was shown that that building fell, and was told that all those who fought against the twelve apostles would likewise fall.
Nephi was then shown the future of his descendants and those of his brothers in the promised land: He saw numerous as the sands of the sea, great wars, contentions, and slaughters, and many cities. He was then shown natural disasters: Darkness, lightnings, thundering, earthquakes, noises, collapsing mountains and broken plains, and cities that were sunken, buried, burned, and shaken down. These were attributed to the judgments of God. The Lamb of God appeared to the survivors, chose twelve disciples among them. (When I was young, I recall puzzled by the reference to their "garments being made white in the blood of the Lamb", but later I understood this to be metaphorical). Three generations and many of the fourth lived in righteousness, but afterwards Nephi's descendants and those of his brothers gathered together in warfare, his own descendants were overpowered and slain, and those of his brothers during and after many generations of warfare, "after they had dwindled in unbelief, they became a dark, and loathesome, and filthy people". (To those who claim this as evidence of Mormon racism, I would reply that this has more to do with the coloring of their souls than of their skins, and I can show evidence of it, later in the book.)
More symbols of Lehi's dream were expounded: there was a fountain of filthy water, and the river Lehi spoke of was also filthiness. The mists of darkness were the temptations of the devil, that harden the hearts and blind the eyes of men, and the building again refers to vain imagination and pride.