Question: what's the difference between parent and child elements? 

Answer: Yup, any object which sits inside another object is a child of that object.  That's all there is to it.  Normally, a child object will inherit the same rights and permissions as the parent object, but you can actually go in and change the permissions.  For instance, say you have a file folder for financial stuff.  The permissions for this folder may be open to all.  Then, inside this folder, you have other folders for each individual person in the house.  These would be child objects of the main folder.  You could then go in and change the permissions so that only that particular person could open that folder and no one else could, even though they all have access to the main folder.  I hope this makes sense.
This question from the Yahoo Q&A forum is categorized in the topic: Entertainment & Music