The Tag Browser works in the same way the Style Browser does.
It will help you to keep track of the assigned tags to your documents. It displays a tree of your tags where tags are nodes and your documents are leafs.
You can see all documents with an assigned tag when opening the first node. If there are documents with more tags, you will see another tag node inside the first on and so on.
By pressing the filter button (
) the Tag Browser displays which tags are not assigned to a document.
Without browsing through your document tree using e.g. the Doqua Navigator you can directly see which tags are not assigned to a document. If there is more than one tag that has not been assigned yet, you can browse the tree as described above.
If you have a large amount of documents, the toolbar button for the currently selected documents (
) will help you. By pressing this button the browser will only display documents from your current selection in a navigator, e.g. Doqua Navigator.