It's actually more of a stuff pack. A new populated world for you to play that was originally available from the Sims 3 Store. It might still be. From what I've heard, the one big complaint that people have about it is that if you have Late Night, EVERY Sim has celebrity status.
ACTUALLY, I already bought this using my phone. My parents don't even know about it. It's one of my little secrets. cool But I need the new Sims 3 patch to use it though. I'll have to ask my dad into install the patch. Then when I'm making my lesbian pirates and my dad sees them kissing, he'll be like 'What is this? If you can make pirates already then why do you want The Sims 3 Barnacle Bay?' lol