a) Piel usually expresses an "intensive" or "intentional" action.
Qal Piel
he broke he broke to pieces, he smashed
he sent he sent away, he expelled
b) Sometimes the Piel introduces a new meaning to the Qal form.
he counted he recounted, he told
he completed he paid, he compensated
he learned he taught
c) Piel expresses a "repeated" or "extended" action.
he jumped he skipped, he hopped
d) Some intransitive verbs in Qal become transitive in Piel.
to be strong to strengthen, to fortify
to become great to make great
(NT only) to listen to the NET Bible 
