Not to be confused with the Ballade. These two are entirely different poetic forms. (The ballad is easier if you ask me, but the ballade is far more elaborate.)
A common ballad is composed of several ballad stazas, or quatrains (four lines) of alternating iambic tetrameter and iambic trimeter. I bet you’re all “WTF are those?” (Again, I will be done with the glossary soon!) In the meantime, look at it this way: An iamb is a metrical foot of two syllables, the first unstressed, the second stressed, like dun-DUN. Unstressed, then stressed, dun-DUN. Since tetrameter means a line with four metrical feet, iambic tetrameter (2 syllables x 4 = 8 syllables) means a line with eight syllables; iambic trimeter (2 syllables x 3) six syllables with alternating unstressed then stressed sounds.
Anyway. Where was I? Oh, yes, a ballad stanza. Four lines. Alternating iambic tetrameter and iambic trimeter. Oh, and it also follows an ABCB rhyme scheme, but some balladeers do ABAB or AABB, too.
How many stanzas does a ballad have? As many or as few as it takes to narrate a story. A ballad in the poetic sense is about narrating a story.
Repetition is also key in a ballad, but it is not required structurally.
’Twas a play on night so frigid
Brought lovers down the bay;
These, the youth, not half so weary
Did perchance bound my way.
Ha! The boys, they tripped and teetered;
“Drunk assholes,” sneered did I.
The maids beneath them shuffled slow—
Till beauty crossed my eye.
A youth was he no younger than
The age of one and twenty.
And lone was he among the crowd;
Saw opportune aplenty.
I winked at him; he flashed a smile—
Soon he and I lay bare
On the deck of my ship a’dock:
A feat that none would dare.
The youth his body fair beneath
In moonlight pallid be;
His lips a’white with so much fright;
I thought he’d shit on me.
I plunged my scepter into him—
Bemoan, he did, aloud!
He gripped my arms; I thrust inside
Of lands that lay unplowed.
He spilt his seed; I spilt my seed—
And kissed beneath the moon.
By dayspring I found naught of he,
And neither aught come noon.