The AO3 Tagging System is a feature of the Archive of Our Own platform that allows users to categorize and describe their fanworks. Tags can include character names, relationships, themes, and content warnings, helping readers find specific types of stories that interest them. Users can create their own tags or choose from existing ones, promoting a diverse range of content. The system also supports filtering, enabling readers to exclude certain tags, which enhances their browsing experience and ensures they find works that match their preferences.