You can tag and categorize similar or related content making it easy to find the content again.
Clicking on a category or tag in the explorer panel displays all content associated with that tag or category.
Tags are unstructured and useful for searches, whereas categories actually help you to structure the organization of your content.
Tags and categories are a form of social indexing, and when a tag and category is created it’s then available across all your sites and can be reused by all users.