What is a Word puzzle or poem in the form of an acronym?

An acrostic is a word puzzle or poem in which the first letters of each line spell out a word or phrase. Here's an example of an acrostic with the word "friendship":

Friends are there to lend a helping hand,

Relax and have fun with you,

Inspire you to be your best,

Every day is brighter with them,

No matter what life throws your way,

Dep in your heart, they'll always stay.

So cherish your friendships,

Hold them close and never let them go,

If you have friends, you have everything.

Peace and happiness will always flow.