Note
This information should be moved to info.tiki.org as per Where.
The fine people at Squiz have prepared a compelling Flash animation:
{FLASH(movie=http://www.youtube.com/v/8XwyhSEqTs0,quality=>high)}{FLASH}
You can show this nice animation to a non-technical person and they will get the picture!
Once you have decided to use a CMS, why choose Tiki?