Categories associate content with keywords for easier searching.
Categories are words or phrases predefined by administrators within a particular place (a space or social group). If there are categories available in the place, it usually means that the place's administrator has given thought to how that place's content should be grouped. An administrator who creates a category can optionally associate certain tags with it behind the scenes.
How do I apply categories?
You can assign categories to your existing or new content. To assign your content to categories: