Cadences are like punctuation in music. They mark the ends of musical phrases and verses, etc in different ways. The
Authentic Cadence gives a strong feeling of finality and comes at the end of most songs. So does the much rarer and softer
plagal cadence, which is also known as the
'Amen Cadence' because of its familiar use when sung by Christian congregations and choirs e.g., A----MEN (
F----C).
The
deceptive cadence (e.g.
G to
A minor in the key of
C) is so called because the music has deceived us into thinking that we're about to go from
G to the home chord of
C but instead we're led to a different chord that we weren't expecting in a kind of 'pleasant surprise'.
Here's a list of some more obscure ones and how they're used.
http://en.wikipedia.org/wiki/Cadence_%28music%29