The Categories tab allows you to manage the categories the product is associated with.
Add Category: This button allows you to select a new category to add the product to. A pop-up window will appear and you can navigate to the desired category in it.
Delete Selected Category: This buttons allows you to remove a product from a category. Select the category or categories by selecting their "Batch" checkbox, then select this button.
Category List: The list of categories the product is included in is shown on the lower portion of the page. Categories may be activated or deactivated by selecting or deslecting the "Active" checkbox. Deactivating a category will keep the product in the category, but it will not appear on the website in that category. Products may be removed from a category by selecting the "Delete" icon for the category.