A Petrarchan sonnet, also known as an Italian sonnet, is a poetic form that consists of 14 lines divided into an octave and a sestet, typically following the rhyme scheme ABBAABBA for the octave and various patterns like CDCDCD or CDECDE for the sestet. This structure is used to explore themes of love, nature, and human emotion, often with a turn or shift in perspective between the two parts.