What is a Collect? The origin of the term collecta, while rather obscure, refers to the “gathering of the people together” as well as to the “collecting up” of the petitions of individual members of the congregation into one prayer. This at first extemporaneous prayer would later also be connected to the Epistle and Gospel appointed for the day. A Collect is a short prayer that asks “for one thing only” (Fortescue) and is peculiar to the liturgies of the Western Churches, being unknown in the Churches of the East. It is also a literary form (an art comparable to the sonnet) usually, but not always, consisting of five parts.
Read more here: “The Collect”
Source: “Introduction.” Zahl, Paul F. M. and Barbee, C. Frederick, eds. The Collects of Thomas Cranmer. Grand Rapids, MI: Wm. B. Eerdmans Publishing Company. 1999. [Kindle Edition]