Foregrounding is a poetic or literary deviced used to draw attention to a particular detail. Foregrounding involves presenting the detail in a manner radically different from the way other information is presented. Foregrounding occurs in poetry when a line or stanza deviates from the structure of the poem. For example, if most the stanzas use rhyming couplets but the last stanza doesn't rhyme at all, our attention will be drawn to that last stanza. In rhetoric, foregrounding can be used for a comic effect. Many jokes foreground a particular character or situation by making it different than the other characters or situations. A common joke setup goes something like this: "a priest, a rabbi and an imam walk into a bar." The priest and rabbi do or say something similar, and the imam does or says something different (and thus funny).
In a literary text, foregrounding highlights ironic elements. For example, in the Oedipus Plays, the fact of Oedipus fulfilling his destiny is foregrounded against the reality of him trying hard not to. Foregrounding is an important literary and poetic device because it forces the reader to challenge his or her assumptions and can thus produce a range of emotions - from surprise to confusion to humor.