How to get there: Go to Settings in the sidebar → Categories tab.
Categories are the portal-wide buckets you use to tag posts by topic (Mobile, Web, API, Billing). They are shared across every board, so a category you create here shows up on Feedback, Roadmap, and Changelog boards alike. Each post belongs to exactly one category.
If you're deciding between categories and tags, see Tags vs categories first.
The category is available immediately on every board.
The color drives the category badge on post cards and, on boards that use the category-columns layout, the column header. Changes apply everywhere the category is shown.
Grab the drag handle (the vertical dots on the left of each row) and drag the category into a new position. Ordering here is the ordering that end users see in the category filter row, filter dropdown, and category columns on every board.
Deleting removes the category and its color from every post that used it. The posts themselves are not deleted; they simply lose the category assignment. There is no undo, so recreate a category with the same name if you want to reverse the action manually.