What's the Difference Between a Blurb and Synopsis?
In short, the biggest difference between the two is the length and the amount of drama.
A blurb is a pitch for your book, often seen on the back of the book's cover. This should not include the conclusion of the book, whereas the synopsis should. The blurb should be anywhere from 500-1000 words, enough to cover the back cover.
A synopsis is a 100-450 word overview of the book. This is what goes on the Amazon description and Barnes and Noble about section of the book. This should include the major parts of the book and a vague description of the ending while leaving enough blanks to make someone want to read it.