An alias is new guise for the same thing. In the context of a gallery, that means a new category for the same image. Aliases in WSN Gallery are used to have a single image appear in multiple categories at the same time. These are not separate images, but a single image making multiple appearances in your gallery.

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

There are also aliases for categories. These allow one category to be a subcategory of multiple different categories.

To add or remove aliases, edit the image or category.