Each listing or category in WSN can have one primary and any number of secondary categories (subject to limits you choose). The versions of a listing/category which are shown in the secondary categories are called aliases, and are exactly the same as the original.

The advantage of using alias instead of copy/resubmit is that when you edit the listing you will always be editing the original listing and all appearances of that listing will instantly be updated with the new information. (If you had merely copied the listing, you would have to edit each separate instance in each category.) Also if the listing is suspended or deleted all references of that listing will be removed from the links directory.

To add or remove aliases, edit the listing or category and see the secondary categories area. Ctrl+click to de-select.