It is used to as a strategy to convince readers of the truth of the writer's position. it is called a claim.

You know Dasher and Dancer

And Prancer and Vixen,

Comet and Cupid

And Donner and Blitzen.

But do you recall

The most famous reindeer of all?

Rudolph, the red-nosed reindeer

had a very shiny nose.

And if you ever saw him,

you would even say it glows.

All of the other reindeer

used to laugh and call him names.

They never let poor Rudolph

join in any reindeer games.

Then one foggy Christmas Eve

Santa came to say:

"Rudolph with your nose so bright,

won't you guide my sleigh tonight?"

Then all the reindeer loved him

as they shouted out with glee,

Rudolph the red-nosed reindeer,

you'll go down in history!