Did you check the posts I linked to (and replied on to you) earlier?
One of the examples is a read-only property that returns someone's full name as a combination of a first and last name; something you can't accomplish with a field.
Another example is, for example, a Discount property on an Order class. It could return the discount based on the current user. E.g.
public int Discount
if (CurrentFictitiousUser == "Imar")
That is, I get a 500 euro discount, while others get just 100.
Finally, for validation, think of an e-mail address (as shown in the earlier posts I mentioned). With a field you can't validate, with a property you can.
Hope this helps. If not, http://en.wikipedia.org/w/index.php?...ns0=1&redirs=0