A chord progression where the subdominant chord is followed by the tonic chord (IV-I). The "IV" represents the chord based on the fourth step of the scale and the "I" represents the chord based on the first step of the scale. The subdominant to tonic progression (IV-I) is also known as an "Amen cadence" or "Church Cadence" because it is sung to the word Amen at the end of Protestant hymns. In the tonality of "C" major, a plagal cadence would be the subdominant (IV) F major chord (F-A-C) moving to the tonic (I) C major chord (C-E-G).
Also Amen Cadence, Church Cadence.