A Petrarchan sonnet, also known as an Italian sonnet, consists of 14 lines divided into two parts: an octave and a sestet. The octave follows a rhyme scheme of ABBAABBA, while the sestet can vary, commonly using CDCDCD or CDECDE. This structure allows for a clear presentation of a problem or theme in the octave, followed by a resolution or reflection in the sestet. The form is named after the 14th-century poet Petrarch, who popularized it. Petrarchan sonnets often explore themes of love, beauty, and nature, making them a favorite among poets throughout history, including Shakespeare and Milton.