It is called Rhyme Scheme ( type: enclose rhyme).
Rhyme is the repetition of sounds in a word used for example at the end of lines of poetry, within a word, in songs, etc.
So as a consequence, Rhyme Scheme is the pattern of rhymes, for example at the end of a poem. They are representing by using letters of the alphabet so that each rhyme in a poem that rhyme with other has assigned a letter (starting with the letter 'A').
Enclose rhyme or enclosing rhyme is the rhyme scheme ABBA. For example:
"Love had us mesmerized under its magic spell A
Our youth's enchanted vision of what life would be B
Innocent intentions that let our lives feel free B
Enraptured in each other's arms as twilight fell." A
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When Oedipus asks the blind prophet for his advice, the chorus is confused because of the answer the prophet provides. He accuses the King Oedipus of being the murderer of the previous king. The chorus are now confused and afraid of the whole situation.
No one can believe that the accusations are truth. They're unsure as to whom they should believe in since phrophets are considered emissaries of the gods and its impossible for them to be mistaken. They now found themselves conflicted.
Hope this helps !