A Petrarchan Sonnet is a 14-line poem that follows a specific rhyme scheme, typically consisting of an octave with an 'abbaabba' pattern and a sestet that varies in form, often using 'cdecde' or 'cdcdcd'. This sonnet form, derived from the works of Italian poet Petrarch, focuses on themes of love, nature, and philosophical contemplation, using its structured form to present a problem followed by a resolution or reflection.