Re: Frequent Flier Miles
You can register with an airlines (in which case they are called "frequent flyer" points/miles) or with a credit card (i.e. 1 mile/point per $ spent). Most airlines have a tie up with a credit card, but there is an annual fee associated with it.
The way it works is that you accumulate enough points by travelling (i.e. JFK-NY to London might get you 9,000 miles or by spending on the credit card :) or both). Once you have enough points you can use it for a free domestic US ticket (need a minimum of 25k points) or keep accumulating and get a free international ticket.
You can also use miles to upgrade from coach class to business class :)