The Italian (or Petrarchan) sonnet can be broken into two parts, the octave (eight lines) and the sestet (six lines). The octave typically rhymes abba abba; the sestet varies, sometimes cdecde, sometimes some variant of that.
The Shakespearean (or English) sonnet is instead three quatrains and a couplet: typically abab cdcd efef gg.
Note: This guide is still in the early stages of development.
Three question marks mean I have to write more on the subject. Bear with me.