Product Attributes can be either made available with All categories and sub-categories, or associated with a specific category.
Under the Associated Category section, decide if you would like to make the attribute available to all the available categories and subcategories, or just to a specific category and its subcategories. If you choose a specific category, the option will only appear on the Listings Manager page when you list an item in that specifice category, or any of its sub-cateogires. An example of a specifice category and sub-category would be; Children, Boys, Tops.