I added descriptions as below, to appear when you mouse over the tag or go to the tag page. Let me know if you have suggestions. Torn between keeping it short and sweet, and providing more detailed context. The categories themselves also have descriptions which are more detailed.
fixed
We prioritize the fixing of bugs in our software reported in the Bug and UX categories. Once bugs are fixed, they are given this tag.
completed
When features suggested in the Feature and UX categories are implemented, they are given this tag.
delivered
When a topic in Marketplace is confirmed delivered by the provider or recipient, it is given this tag.