The sonnet is the name of the most well-known 14-line poem type; however, not all 14-line poems have names. There are two main types of sonnets: Shakespearean and Petrarchan, or Italian and English, respectively.
The 14-line Petrarchan sonnet, so named after its creator Petrarch, is divided into two sections: an octave (the first eight lines), followed by a sestet (the next six lines). While the rhyme pattern of the sestet changes, the octave has a fixed rhyme scheme of ABBAABBA.
Shakespeare changed the sonnet to make it grammatical in English. The Shakespearean sonnet is divided into three groups of four lines known as quatrains, and a final couplet. Shakespeare’s sonnet is written in iambic pentameter and contains the rhyme pattern ABABCDCDEFEFGG.