How is the Shakespearean sonnet different from the Petrarchan sonnet?Other than the structure, what are the differences?

Originating in Europe, the word
sonnet derives from the Occitan word "sonet" and the
Italian "sonetto," both of which means "little song or sound." Here are the main
differences between the Shakespearean and Petrarchan sonnet
forms.

The Shakespearean style
of sonnet usually contains 14 lines following a specific rhyme scheme and structure.
Shakespeare's' sonnets all contain ten syllables per line and are written in
iambic pentameter, 

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in which a pattern of an unemphasized syllable
followed by an emphasized syllable is repeated five times. The rhyme scheme in a
Shakespearean sonnet is a-b-a-b, c-d-c-d, e-f-e-f, g-g; the last
two lines are a rhyming
couplet.

Not all poets follow
the specific metrical structure, since some sonnets contain 12 syllables per
line.

Petrarchan sonnets,
usually first credited to Giacomo da Lentini, were popularized by the Italian Petrarca
(or Petrarch). They usually consist of two parts forming
a 

compact
form of "argument". First, the octave (two quatrains), forms the "proposition" which
describes a "problem", followed by a sestet (two tercets), which proposes a resolution.
Typically, the ninth line creates what is called the "turn" or "volta" which acts to
signal the move from proposition to resolution. Even in sonnets that don't strictly
follow the problem/resolution structure, the ninth line still often marks a "turn" by
signaling a change in the tone, mood, or stance of the poem. In the sonnets of Giacomo
da Lentini, the octave rhymed a-b-a-b, a-b-a-b; later, the
a-b-b-a, a-b-b-a pattern became the standard for Italian sonnets.
For the sestet there were two different possibilities, c-d-e-c-d-e
and c-d-c-c-d-c. In time, other variants on this rhyming scheme
were introduced such as
c-d-c-d-c-d.