Categories are managed from the Products > Product Categories screen. Just like post categories, you can add, delete and edit your categories here.
Categories can also be re-ordered by dragging and dropping them – this order will be used by default on the frontend whenever the categories are listed. This includes both widgets and the subcategory view on product pages.
Product tags work in exactly the same way as post tags. See http://codex.wordpress.org/Posts_Tags_Screen
Attributes are pieces of data which can add more technical information to a product and help users further refine your catalog while browsing / searching. Creating an attribute set is done in a similar way to a category (we’ll get to that later). For now we’ll describe attributes and their primary benefit with a hypothetical example.