I have a Pinterest account merely for seeing the application and having some vague understanding of how it works. Being an account owner, I received the email notification for this change, which is omitted from this link.

  Our original Terms stated that by posting content to Pinterest you grant Pinterest the right for to sell your content. Selling content was never our intention and we removed this from our updated Terms.

  We updated our Acceptable Use Policy and we will not allow pins that explicitly encourage self-harm or self-abuse.
 
  We released simpler tools for anyone to report alleged copyright or trademark infringements. 

  Finally, we added language that will pave the way for new features such as a Pinterest API and Private Pinboards.

I thought they did a nice job summarizing and convey in a concise, understandable way, the changes they've made.