The point of doing this is just to make it a little faster when you are adding new products. It is completely optional.
If you associate this template with a product category, then whenever you add a new product of that category, the product will by default be set to display with this template, although you can always change it. (However, if you add a new product and put it in more than one category, then this template might not end up being the default for that product.)
This template may be associated with as many categories as you like.
Currently this template is associated with the
category(ies): This template has not yet been associated with any categories. All categories are associated with this template. There are none left to add!
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