Noun

piece of hanging or attached material

https://www.merriam-webster.com/dictionary/tags

Guidelines for blogging on the Openlab

“much like a table of contents and an index, categories and tags”

Tags has many definitions so i decided to pick this word to look up to see which definition is being used here. The one that i found that makes the most sense here is one i used above. To make a post we use tags to have other related material be attached as well.