I admit that the terminology might not be obvious at first blush to some aspirants.
* "First Class" - the folks who pay more for their seats. They usually (on US carriers definitely) get wider, better seats with more leg room, free booze, better food, better entertainment, etc.
* "Coach" - Otherwise known as the cattle car.
Where everyone else sits.
* "Flat Price" - Everyone (in a given class) pays the same rate for their ticket. Some airlines charge different amounts based on how close to your travel date your book - the specs are simplifying it by stating that the person who decides 2 hours in advance to fly gets the same rate as the person who decided 2 months in advance.
And it's not a trivial question - as you pointed out, it helps you understand the matter and that's critical to being a software architect.
[ August 24, 2007: Message edited by: Theodore Casser ]