A proverb is usually a statement that expresses some universal bit of
wisdom. It is normally a very old expression that has come down
to us through the years because it encapsulates some truth in a very
succinct and clever way. It may not be very obvious what the
meaning is because proverbs are sometimes very metaphorical.
A stitch in time saves nine. (Proverb.)
(Literal meaning: If there is a small tear in some article of
clothing, repair it with one stitch - using needle and thread -
before it gets bigger and requires nine stitches to repair.
Proverb meaning: It is better to take care of a problem or
troublesome situation before it becomes an even greater problem that
will be even more difficult to solve.)
An idiom is simply a group of words with a meaning of its own which
cannot be inferred from the meaning of the separate words that it is
composed of.
Because of the extreme heat, my pet iguana kicked the bucket. (This is obviously not a proverb.)
(Idiom:
to kick the bucket = to die)
CJ