In the Calculated Metric Manager, tagging segments allows you to organize them.
All users can create tags for calculated metrics and apply one or more tags to a metric. However, you can see tags only for those calculated metrics that you own or that have been shared with you. What kinds of tags should you create? Here are some suggestions for useful tags:
In the Calculated Metric Manager, mark the checkbox next to the metric you want to tag. The management tool bar appears:
Click Tag and either
select from existing tags, or
add a new tag name in the Add Tags/Search dialog box and press Enter.
Click Tag again to tag the metric.
The tag should now appear in the Tags column. (Click the gear icon on the top right to manage your columns.)
You can also filter on tags by going to Show Filters > Tags.