Tags are a tool to organize, categorize and later find bookmarked stories in the library.
Lists, types and keywords did the same thing, but in a rigid way. Stories could have only one 'Type', could belong to unlimited lists and could have any keyword that you wanted. However, access to keywords was limited to the search field on the left.
Tags are the same thing as all three, but the new interface is simpler to deal with, No unnecessay complicated management tools (that nobody seemed to use), and they're available anywhere in the library and in the bookmarking form. They easy to use and very convenient.
Simple.
After you click the bookmark button for a story anywhere on the site you get this form:

It used to have the Lists' field, the Types' menu and at the bottom the field for keywords.
Now it has the 'My Rating' menu, the Queue check box and the option notes fields, and below all that, the tagging facilies. The above picture shows form for a user that never used any tags before. The tagging facilities are empty.
To start using tags, just type some tags into the 'New Tags' field, separating individual tags with commas.

The words 'My First Tags' and 'My Second Tag' could be replaced with anything you fancy, like 'Really Hot Stories' or 'Futuristic Stories' whatever you want to use, you can. You can use one tag, ten tags, or even none. It's up to you.
Once you entered some tags, click the 'Add story' button and the story will be added to your library.
The next time you bookmark a story, the tags that you've used previously will be already available in the form.

To add one of your previously used tags to the story you're bookmarking, just click the tag and it will jump to the top line.


If you need to remove a tag from story click the 'X' in the tag on the top line. That will move the tag to the bottom line.
Once you have used the tags, the library will remember your tags.
To use the tags to find stories, simply select the tag from the 'Show Tag' menu in the library.

And the tagged stories will be displayed.

Simple:
Select the stories that you want to tag. It could be one or more. To tag all the stories in an old list, go to the list and click the 'Toggle Selection' link at the bottom, that will select all the stories. Then click the 'Tag Selected...' button.

That will show you the batch tagging form.
You can add tags to the stories' tags. You can completely erase the stories tags and replace them with the selection. Or, you can remove tags. Just select the appropriate radio button.