What qualifies a poem to be Petrarchan sonnet rather than another type of sonnet?

The sonnet is split in two groups: the "octave" (of 8 lines) and the "sestet" (of 6 lines), for a total of 14 lines.

The octave (the first 8 lines) typically introduces the theme or problem using a rhyme scheme of abba abba. The sestet (the last 6 lines) provides resolution for the poem and rhymes variously, but usually follows the schemes of cdecde or cdccdc.