Meaning of Exoteric and Esoteric

ex·o·ter·ic
Exoteric refers to knowledge that is outside of and independent from anyone's experience and can be ascertained by anyone. Exoteric relates to "external reality" as opposed to one's own thoughts or feelings. It is knowledge that is public. It is not required that exoteric knowledge come easily or automatically, but it should be referenceable or reproducible.
adj. 1. Not confined to an inner circle of disciples or initiates. 2. Comprehensible to or suited to the public; popular. 3. Of or relating to the outside; external.

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es·o·ter·ic
Esoteric relates to spiritual knowledge, and comes from "within", thus "pertaining to the more inward", mystic, and is of a mysterious nature.
adj. 1. a. Intended for or understood by only a particular group. b. Of or relating to that which is known by a restricted number of people. 2. a. Confined to a small group: esoteric interests. b. Not publicly disclosed; confidential.

Early Christian Church Father Origen wrote, "In these circumstances, to speak of the Christian doctrine as a secret system, is altogether absurd. But that there should be certain doctrines, not made known to the multitude, which are (revealed) after the exoteric ones have been taught, is not a peculiarity of Christianity alone, but also of philosophic systems, in which certain truths are exoteric and others esoteric. (Origen, Against Celsus 1.7, in ANF, 4:399.)

Latter-day Saint writings allude to a similar practice. Consider the following passages from the Book of Mormon prophet Alma and the apostle Joseph Fielding Smith:
"And now Alma began to expound these things unto him, saying: It is given unto many to know the mysteries of God; nevertheless they are laid under a strict command that they shall not impart only according to the portion of his word which he doth grant unto the children of men, according to the heed and diligence which they give unto him. And therefore, he that will harden his heart, the same receiveth the lesser portion of the word; and he that will not harden his heart, to him is given the greater portion of the word, until it is given unto him to know the mysteries of God until he know them in full. And they that will harden their hearts, to them is given the lesser portion of the word until they know nothing concerning his mysteries." (Alma 12:9— 11)

he early Jewish Christian Clementine Recognitions says, "For the most sublime truths are best honoured by means of si-lence." (Peter, in Clementine Recognitions 1.23, in ANF, 8:83.)

A related document, the Clementine Homilies, says that "it would be impious to state the hidden truths" to the wicked. (Clementine Homilies 19.20, in ANF, 8:336.)

Ignatius told the Roman Christians, "I am able to write to you of heavenly things, but I fear lest I should do you an injury. Know me from myself. For I am cautious lest ye should not be able to receive [such knowledge], and should be perplexed." (Ignatius, Romans 9, in ANF, 1:104, brackets in original.)

The Clementine Recognitions advocated using a "certain circumlocution" (rather than direct explanations) to hide the holiest truths from the profane, who would weary God's servants with their worldly arguments. "But if he set forth pure truth to those who do not desire to obtain salvation, he does injury to Him by whom he has been sent, and from whom he has received commandment not to throw the pearls of His words before swine and dogs, who, striving against them with arguments and sophisms, roll them in the rand of carnal understanding, and by their barkings and base answers break and weary the preachers of God's word." (Clementine Recognitions 3.1, in ANF, 8:117.)

Writings from the Dead Sea Scrolls and the Nag Hammadi Codices show that for two centuries after Jesus Christ, certain religious groups practiced sacred rituals that were to be kept secret from others (See Esoteric Ritual During the New Testament Era)

Also See:
Them Sneaky Early Christians
A review of "Hidden Wisdom: Esoteric Traditions and the Roots of Christian Mysticism"
Hidden Wisdom: Esoteric Traditions and the Roots of Christian Mysticism