How the tagging system work in Forem?

Hello Dev Community!
I am building a Rails App and I need to add a tagging system for articles. I tried to analyze how tagging works in Forem but it's quite hard to understand the logic.

I see there is an index in the Article table called cached_tag_list. I guess the idea is to have a bridge between the Tags table and the Articles table, with a connection table for each article with a specific tag (article_id, tag_id).

Can anyone explain to me the logic to create an efficient tagging system with Rails? Thanks.