A sonnet is a single stanza poem which comprises of fourteen lines, written in an Iambic pentameter. A simple grouping of syllables, stressed and unstressed, is called a foot. One way to describe a verse line is to talk about how many stressed and unstressed syllables are in the line.The Iambic foot is an unstressed syllable followed by a stressed syllable. Whereas pentameter means that there are five feet in the line .So, "Iambic Pentameter," therefore means a line of ten syllables alternating stressed and unstressed syllables according to the Iambic rhythm.
When a pattern is formed by the rhyming words at the end of each line then it is known as rhyming scheme of a sonnet. Each end rhyme is assigned a letter, and thus the fourteen letters assigned describe the rhyme scheme of the sonnet. Moreover , different kinds of sonnets have different rhyme schemes.
The Petrarchan sonnet has rhyme scheme as 'ABBAABBA CDECDE ' which is named after the fourteenth century famous Italian poet ,Petrarch.The first eight lines all end in either rhyme A or B, form the octave. Whereas the last six lines end with C, D, or E, form the sestet. There is usually a pause or break in between the octave and sestet which is known as the volta or turn. Traditionally, one main problem is set out in the octave and brought to a resolution in the sestet.
In the sixteenth century the English or Shakesparean sonnet was developed by the Earl of Surrey