The Restored Gospel & Christian History Lesson 17 & 18

The Guide to the scriptures defines a Seer as:

"A person authorized of God to see with spiritual eyes things that God has hidden from the world (Moses 6:35–38). He is a revelator and a prophet (Mosiah 8:13–16). In the Book of Mormon, Ammon taught that only a seer could use special interpreters, or a Urim and Thummim (Mosiah 8:13; 28:16). A seer knows the past, present, and future. Anciently, a prophet was often called a seer (1 Sam. 9:9; 2 Sam. 24:11).

Joseph Smith is the great seer of the latter days (D&C 21:1; 135:3). In addition, the First Presidency and the Council of the Twelve are sustained as prophets, seers, and revelators."

Because of Joseph Smith we know:

1. God the Father and His Son, Jesus Christ, are two separate, distinct beings. The Bible confirms Joseph Smith’s discovery. It tells us that the Son submitted His will to the Father (see Matthew 26:42).
2. The Father and the Son have glorified bodies of flesh and bones. Following the Savior’s Resurrection, He appeared to His disciples and said, “Handle me, and see; for a spirit hath not flesh and bones, as ye see me have” (Luke 24:39).
3. God still speaks to man today—that the heavens are not closed. 
4. The full and complete Church of Jesus Christ was not then upon the earth. Of course there were good people and some components of the truth, but the Apostle Paul had anciently prophesied that the Second Coming of Christ would not come “except there come a falling away first” (2 Thessalonians 2:3).Through Joseph Smith was restored the doctrine of the gospel being preached to the dead in the spirit world to those who did not have a fair chance on earth to hear it (see D&C 128:5–22; see also D&C 138:30–34). 
5. Joseph Smith restored the truth that there are multiple heavens.

"Through Joseph Smith have been restored all the powers, keys, teachings, and ordinances necessary for salvation and exaltation. You cannot go anywhere else in the world and get that. It is not to be found in any other church. It is not to be found in any philosophy of man or scientific digest or individual pilgrimage, however intellectual it may seem. Salvation is to be found in one place alone, as so designated by the Lord Himself when He said that this is “the only true and living church upon the face of the whole earth” (D&C 1:30)." Elder Tad R. Callister

This information is from Elder Callister's talk Joseph Smith-Prophet of the Restoration