Tags lists every custom tag defined in your tenant, a working set here includes severity tags like Critical, High, Medium, and Low, and workflow tags like Hazmat, Requires QA, Backordered, Drop-Ship, Service/Subscription, and Needs Review. Tags can be assigned to individual PO lines (see the Tag column in Purchase Order's Details View) to categorize and filter them however your workflow needs.
Creating a tag
Create New opens a "Create a Tag" form with a Title and a Color, so tags stay visually distinguishable wherever they're shown.

Columns
The list shows the Tag itself, Created On, and row-level Action options. Use Copy / Download CSV / Print to export the current list.