The Post Attributes module in Editor allows you to set categories and tags for your posts.
Categories vs. Tags
Categories and Tags provide a helpful way to group related posts together, and to quickly tell readers what a post is about. Categories and Tags also make it easier for people to find your content.
Categories are used to define sections of your site and group related posts. The default category is “Uncategorized” until you change it in your writing settings.
Tags are similar to categories, but they are generally used to describe your post in more detail. Unlike categories, tags have no hierarchy, meaning there’s no relationship from one tag to another. The use of tags is completely optional.
What’s the difference between categories and tags?
Normally, tags are ad-hoc keywords that identify important information in your post (names, subjects, etc) that may or may not recur in other posts, while categories are pre-determined sections. If you think of your site like a book, the categories are like the Table of Contents and the tags are like the terms in the index.
A basic rule of thumb is to select ONLY ONE category, but use many tags.