Each community in PieFed can have it's own set of "flair" options that posters can attach to their posts. Clicking on a flair will filter the community to only show posts with that flair so they function as a filtering mechanism as well as a visual identifier.
Community moderators can manage the flair that are available in their communities:
When creating posts, expand the 'more options' area to assign one or more flair to your post:
See it in action at https://piefed.social/c/piefed_meta
Flair doesn't federate yet but it will in coming days.