A pitch -- notice it has PITCH -- is in fact a verbal synopsis of your novel, but there is no rule that says a pitch can't be the synopsis and visa versa. A pitch/synopsis can be seen as precisely the copy you'd want to see on the backflap of a hardcover or backside of a paperback. The one with your title and name on it.
The synopsis-pitch is the most important short-short you will ever write - the story of your story and a sales pitch for the book. Not everyone is comfortable with a "bragg" of any sort on their own books, but done professionally and cleanly, it does not have to sound filled with hubris.
Most published works have backflap copy written by a copyeditor who can be more objective and direct and write in the voice of a cheerleader that touches on Who, What, Where, When, How or Why or all six Journalistic requirments. That is main character (whose story is it anyway?). Zero in on precisly WHO is central to the story, who is the fulcrum around which all satelite characters orbit, and then speak of him or her by name and occupation. Follow up with setting, time, what's the main storyline or goal or obstacle or a combination of these - the how and the why of it.
And it needs be about as short as my remarks here, if not shorter. Check out descriptions on ebooks for samples where many have been done by Indie authors and not copy editors, and do the same with paperbacks at the local drugstore. Ingest and own the style of the copyeditor who knows how to say MORE with far LESS than most of us. Finally, get hold of my Dead On Writing for all manner of issues in publishing, about craft, and ebooks as well as paper.
Robert W. Walker
Dead On Writing (Amazon Kindle & Wordclay.com for POD)