difference in technorati tag and just a group of category names?

i have read several places that search engines and technorati pick up wordpresses tags very easily.

what is the difference between these tags and just listing your categories on a page somewhere?

 

i think there is no difference between those tags and the other

 

i dont see why it would be either, but everywhere i read , i see, "technorati picks up the wordpress tags" or Google loves tags

well why aren't my menu items of sections considered tags, or if i have the section and category name links under my article name....are those not tags