1. Webmaster Tools shows Google errors and problems like duplication from pagination where the URL changes by adding the page number.
2. Tags are smaller in scope than categories and are focused keywords for topics in a post, like "Chicken, Meat, Fish" for food categories.
3. Categories allow organization of website posts and creation of breadcrumbs for navigation from broad to specific pages like "Home > Blog > Arabic Food > Soups > Red Soup".