This is a Spanish form of eight syllable (Iambic Tetrameter) lines. The rhyming scheme can vary in presentation ie a.a.b.b.a, a.b.b.a.a. etc but only two consecutive lines may have the same rhyme scheme.
In the Example below, the poet uses two couplets and links back to the starting rhyme in this very graphic poem:
a flickering flame, on the wall
the sound of a, coyotes call
the desert winds, singing at night
sandstorms dancing, in the moonlight
embracing lovers, to befall
Here is a lovely example by Sharon where she uses a rhyme scheme of, a.b.b.a.a.
Your quiet cries echo loudly with pain
I feel you suffer in silence
Honest open hearts lend true credence
Comfort found in friendships gained
Toss me the key, let's free your chains