I did this in September for the same reason. Our offer was if we put $500 on the card, we'd receive 30,000 "bonus points". When I called for more information, I discovered the way it works.
For every $1 you spend, you accrue 1 point. When you want to redeem your points, you get them in the form of a statement credit towards travel expenses that you put on your AMEX card that month. For every $100 you want credited, it will cost you 7500 points. You are earning at a rate of 1.25%.
For example, you buy a plane ticket for $250 and charge it to your AMEX card. When the statement comes, you apply for a credit for that purchase. You can either redeem 15,000 points ($200) or 22,500 to cover the entire $250 purchase. You must redeem in 7500 increments and you only get credit for the exact amount of the purchase if it is less than your redemption amount.
We received 30,000 bonus points which calculated into $400 in travel expenses. The points never expire and we've accrued another $100 for our upcoming trip. The nice thing is that it is for anything that AMEX categorizes as "travel". This includes hotels (i.e. Disney!), rental cars, airline charges and anything bought via a
travel agent (i.e. Disney packages!). I even found out that I can apply the rewards to park passes from
undercovertourist.com!
I pay the balance off every month but I believe that this AMEX card allows you to carry a balance. With no annual fee and the "free" $400 right off the bat, it was too good of an offer to resist, especially since we only have one other credit card.
In your situation, the "2 free airline tickets" probably refers to redemption of 30,000 points for 2-$200 tickets. That's just a guess. Also, the bonus points take a few statements to show up. I wouldn't charge anything that you want to redeem points for until a couple months after you have the card. I think it took 3 statements before our bonus points showed up.