There'll probably be Eric Musco (community manage, you might have seen him here on the forum or on some livestreams) + 2 developers around. It usually starts with a welcome and then they give infos about what's coming up / news. There's also questions and answers, a quiz where you can win some goodies... uuhh...
After about 1 - 1 1/2ish hours the "official" part is over. Thn you can get free food and drinks (for 2 hours or so, after that you have to pay) and it's just "hanging around" with the above mentioned folks, talking with them about all and everything you can think of, not just SWTOR^^