Dictionary.com

1. acknowledgment; avowal; admission: a confession of incompetence.
2. acknowledgment or disclosure of sin or sinfulness, especially to a priest to obtain absolution.
3. something that is confessed.
4. a formal, usually written, acknowledgment of guilt by a person accused of a crime.
5. Also called confession of faith. a formal profession of belief and acceptance of doctrines, as before being admitted to church membership.
6. the tomb of a martyr or confessor or the altar or shrine connected with it.

Etymonline.com

late 14c., confessioun, “action of confessing, acknowledgment of a fault or wrong,” originally in religion, “the disclosing of sins or faults to a priest as one of the four parts of the sacrament of penance,” from Old French confession (10c.), from Latin confessionem (nominative confessio) “confession, acknowledgement,” noun of action from past-participle stem of confiteri “to acknowledge” (see confess).

An Old English word for it was andettung, also scriftspræc. Meaning “that which is confessed” is mid-15c.  Meaning “a formula of the articles of a religious faith, a creed to be assented to” is from late 14c. In the common law, “admission or acknowledgment of guilt made in court or before a magistrate,” 1570s.

Discussion/Explanation

The descriptions above do a great job of describing this term. I do want to highlight a few points.

The term reads “confessions” rather than “confession” as this post is truly aimed at what is also called “confessions of faith”. Creeds are related to this term.

The second part of the etymonline description speaks on this point. I want to add that each confession that arose was primarily in response to opposing beliefs at the time of writing. Typically, these opposing beliefs were heresies and the confession arose as a written document of faith that clearly defined what the faith was in contrast. The Nicene Creed and Apostles Creed are examples that arose during such times.

These creeds served as summations as well as building blocks to more comprehensive writings more commonly called a “confession of faith”. As such, creeds have gone hand-in-hand with confessions though you won’t hear a church recite an entire confession as they are often book-length whereas a creed is much shorter (a summation as said earlier).

Some common confessions would include:

• The Westminster Confession of Faith
• The 1689 London Baptist Confession of Faith (also called the 2nd London Baptist Confession)

These confessions were never meant to replace the Scriptures and often quote them and give references to specific passages. They serve as teaching tools and clarifying tools as they often pull together the greater context of the counsel of God found in His Word (the Bible).