Chords are made up of three or more notes played simultaneously. Chords give music a tonal center for the melody, and Roman numerals (such as I, IV and V) are used to refer to chords describe the root (bottom) note of the chord in relation to the first note of the scale.
Music is driven by chord movement. Chords give music a tonal center, and chord progressions give music originality and richness. Different types of cadences are actually just different arrangements of the last chords in a progression.
The perfect authentic cadence is the most common type and is most often found at the end of a piece. The chord progression of this cadence is V-I.
Compared to the perfect authentic cadence, the plagal cadence is a slightly weaker ending. The progression of this cadence is IV-I, and it is often used mid-piece to transition from one phrase into the next.
This cadence uses the V chord to anticipate the I chord; instead of resolving down, however, this cadence goes from V-vi. A deceptive cadence can be used to bring richness to a pattern or to elongate a musical thought.