I tried to explain above by talking about tones and semitones rather than giving the "white key" description, but as it's been called silly, I think it's only fair to mount a prinicipled defence: The white key explanation is useful for anybody with access to a keyboard to sit down and play through the different modes and HEAR how different they are. Basically it's the easiest way to get a sense of the different flavours.

You can write pages and pages and that's all very useful for getting a technical and in depth understanding, but the most simple "hear it for yourself" method is the white key one.