But what does that mean? To me, this is a child born from Harry Potter, YouTube, 4Chan and the Kindle. it sounds to me like a website where you can read the Harry Potter books (for a fee?) and watch animated content. Jo described it as a "digital generation you'll enjoy" and a "unique experience built around the books". She also said she'll be sharing information about the Harry Potter world that she's been holding onto for years.
I have to admit, I'm not overly psyched for this new information. I want it to be awesome scenes with Snape being brave and chivalrous, but the odds are against that. More likely, it will be as important as "Quidditch Through the Ages".
The animated content could be pretty awesome. It eliminates the need for child (awful) actors, and your characters age when you decide they should. Seriously, how old is Dan Radcliffe? I'm guessing here, but it sounds like users will be able to add videos, too. Exciting for people who have that skill!
JKR also announced The Harry Potter books will be available in e-book form. However, she didn't list any specific platforms.
Pottermore will be open sometime in October. A lucky few will have a chance to get in early, you just need to check back on July 31 to find out how.