Definition: A stanza of a poem equals to a paragraph of an essay, without the indentation.
Example:
Birdfoot's grampa
The old man
must have stopped our car
two dozen times to climb out
and gather into his hands
the small toads blinded
by our lights and leaping,
live drops of rain.
The rain was falling,
a mist about his white hair
and I kept saying
you can’t save them all
accept it, get back in
we've got places to go.
But, leathery hands full
of wet brown life,
knee deep in the summer
roadside grass,
he just smiled and said
they have places to go to
too.
~ Joseph Bruchac~
Significance: Stanza doesn't necessarily be include in every poem, but it is important when you write a long poem. You wouldn't find tedious when reading a long poem with stanzas, because it makes you stop and think back on what you read. Also, each stanza is like a paragraph in an essay, having difference ideas at a time.