D&C 21

In a world of cynics, this revelation that was given on the day the Church was organized must be very difficult.  But yet, understanding that this is really the Lord's truely restored Church, the Savior followed much the same historical pattern in declaring His chosen Prophet.  The burden to know this is true falls on the believer.

Herein the Lord instructs the Prophet Joseph Smith -

BEHOLD, there shall be a record kept among you; and in it thou shalt be called a seer, a translator, a prophet, an apostle of Jesus Christ, an elder of the church through the will of God the Father, and the grace of your Lord Jesus Christ..."  (Doctrine and Covenants | Section 21:1)

To the Prophet, this must have been very humbling.  To better understand what a seer, a translator, a prophet, and an apostle is, I quote from the writings of David J. Ridges -

Seer

Elder John A. Widtsoe defined a seer as “one who sees with spiritual eyes. He perceives the meaning of that which seems obscure to others; therefore he is an interpreter and clarifier of eternal truth. He foresees the future from the past and the present. This he does by the power of the Lord operating through him directly,
indirectly with the aid of divine instruments such as the Urim and Thummim. In short, he is one who sees, who walks in the Lord’s light with open eyes” (Mosiah 8:15–17). (Evidences and Reconciliations, 1:205–6; see also Moses 6:36.)

Translator

The title “translator” may refer to one who has received two blessings given a prophet by the spirit of God: 1. The power to convert the written or spoken word into another language (see D&C 20:8). 2. The power to give a clearer meaning to a given language. Through the gift of translation a prophet does not merely convey in the language of the reader the words that were recorded by the writer but by revelation preserves for the reader the thoughts or intent of the original writer.

Prophet

According to Elder Widtsoe, “ A prophet is a teacher. That is the essential meaning of the word. He teaches the body of truth, the gospel, revealed by the Lord to man; and under inspiration explains it to the understanding of the people. He is an expounder of truth. Moreover, he shows that the way to human happiness is through obedience to God’s law. He calls to repentance those who wander away from the truth. He becomes a warrior for the consummation of the Lord’s purposes with respect to the human family. The purpose of his life is to uphold the Lord’s plan of salvation. All this he does by close communion with the Lord, until he is ‘full of power by the spirit of the Lord.’ (Micah 3:8; see also D&C 20:26; 34:10; 43:16) “In the course of time the word ‘prophet’ has come to mean, perhaps chiefly, a man who receives revelations and directions from the Lord. The principal business of a prophet has mistakenly been thought to foretell coming events, to utter prophecies, which is only one of the several prophetic functions. “In the sense that a prophet is a man who receives revelations from the Lord, the titles ‘seer and revelator’ merely amplify the larger and inclusive meaning of the title ‘prophet.’” (Evidences and Reconciliations, 1:204–5.)

Apostle

An Apostle is a special witness of Jesus Christ to all the world (see D&C 107:23). The Prophet Joseph Smith explained the important calling of an Apostle by asking a question and then giving the answer: “What importance is there attached to the calling of these Twelve Apostles, different from the other callings or officers of the Church? . . . “They are the Twelve Apostles, who are called to the office of the Traveling High Council, who are to preside over the churches of the Saints, among the Gentiles, where there is a presidency established; and they are to travel and preach among the Gentiles, until the Lord shall command them to go to the Jews. They are to hold the keys of this ministry, to unlock the door of the Kingdom of heaven unto all nations, and to preach the Gospel to every creature. This is the power, authority, and virtue of their apostleship.” (History of the Church, 2:200.)   (Ridges, David J. (2004-12-01). Doctrine and Covenants Made Easier Volume 1 (Kindle Locations 3014-3021). Cedar Fort, Inc.. Kindle Edition.)