Sonnets are fourteen lines poems divided into octet and sestet. Octet means eight lines and sestet means six lines. These were popular in Italian and were later introduced in English by Sir Thomas Wyatt. In Italy it was made popular by Italian poet Francesco Petrarch. It's classic rhyme scheme is ABBA ABBA CDE CDE but other variations exist. Sonnets that use this classic rhyme are called Petrarchan sonnets. Hence, Petrarchan is a category of sonnet.