The terms have many definitions. Here are some from Dictionary.reference.com.
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Por·nog·ra·phy
n.
1. Sexually explicit pictures, writing, or other material whose primary purpose is to cause sexual arousal.
2. The presentation or production of this material.
3. Lurid or sensational material:
"Recent novels about the Holocaust have kept Hitler well offstage [so as] to avoid the ... pornography of the era" (Morris Dickstein).
Also:
Books, photographs, magazines, art, or music designed to excite sexual impulses and considered by public authorities or public opinion as in violation of accepted standards of sexual morality. American courts have not yet settled on a satisfactory definition of what constitutes pornographic material.
A⋅dul⋅ter⋅y
–noun, plural -ter⋅ies.
Voluntary sexual intercourse between a married person and someone other than his or her lawful spouse.
Also:
1. The unfaithfulness of a married person to the marriage bed; sexual intercourse by a married man with another than his wife, or voluntary sexual intercourse by a married woman with another than her husband.
Note: It is adultery on the part of the married wrongdoer. The word has also been used to characterize the act of an unmarried participator, the other being married. In the United States the definition varies with the local statutes. Unlawful intercourse between two married persons is sometimes called double adultery; between a married and an unmarried person, single adultery.
2. Adulteration; corruption. [Obs.] --B. Jonson.
3. (Script.) (a) Lewdness or unchastity of thought as well as act, as forbidden by the seventh commandment. (b) Faithlessness in religion. --Jer. iii. 9.
4. (Old Law) The fine and penalty imposed for the offense of adultery.
5. (Eccl.) The intrusion of a person into a bishopric during the life of the bishop.
6. Injury; degradation; ruin. [Obs.]
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So pornography are materials that elicit the reaction of adultery (as understood as moral corruption) in a person. The terms mean differently of course, but they are related.