Theory:

A Refrain, is a phrase, line, or group of lines repeated at intervals in a poem, at the end of the stanza.
Example:
Little Sarah she stood by her grandmother’s bed,
“And what shall I get for your breakfast?” she said;
“You shall get me a Johnny-cake: quickly go make it,
In one minute mix, and in two minutes bake it.”
So Sarah she went to the closet to see
If yet any meal in the barrel might be.
The barrel had long time been empty as wind;
Not a speck of the bright yellow meal could she find.

But grandmother’s Johnny-cake-still she must make it,
In one minute mix, and in two minutes bake it.
Here in  the poem "Little Sarah" the refrain is: In one minute mix, and in two minutes bake it.
Narrative poetry is a form of poetry that gives a story, using the voices of a narrator and characters both and the plot.
Example:
Little Sarah she stood by her grandmother’s bed,
“And what shall I get for your breakfast?” she said;
“You shall get me a Johnny-cake: quickly go make it,
In one minute mix, and in two minutes bake it.”
So Sarah she went to the closet to see
If yet any meal in the barrel might be.
The barrel had long time been empty as wind;
Not a speck of the bright yellow meal could she find.

But grandmother’s Johnny-cake-still she must make it,
In one minute mix, and in two minutes bake it.
Here in this poem "Little Sarah" the narrator is narrating little Sarah as "she":
 
Little Sarah she stood by her grandmother’s bed...
So Sarah she went to the closet to see