glad it has worked out for you & your kids, tishie, but i personally agree with age-appropriate truth on this one.

thunderbear - my guess is your son only wants a very brief answer, not all the details - just something small to sate his curiosity!! so maybe like the answer rainbowzz posted for 3-6 year olds would be enough. as you've already found out, the more you try to avoid an answer, the more you kid's curiousity will grow. nip it in the bud with something simple, and he will probably forget what it means soon enough anyway .