Reference : Attribute types : Tag
  
Tag
The tag attribute can hold tag key words that can be used to tag elements. Customers can use existing tags or create new tags while editing a tag attribute. Tags are useful for filtering, searching, and grouping elements.
Tag settings
 
Setting
Name and description
Value
You can configure the following settings:
Default Value: The value for the attribute for a new element.
Allow Group By: Enables the tag attribute to be used to group elements in tree structures in a Display view.
Change Log
You can configure the following setting:
Log Changes: Records each change of the attribute value.
Additional settings
By default, the scope of a tag attribute will be limited to that attribute alone. This means, if you have two tag attributes in the workspace, both of them would maintain an individual set of keywords. This behavior can be changed by the "Scope of tag keywords" setting under Configure > Workspace. If you set the scope as "workspace level" then all the tag attribute will maintain a single cloud and the tags created in one attribute will be visible while editing another tag attribute.
By default, a normal user will be able to create new tags while saving a tag attribute. This behaviour can be controlled using the setting "Disable Add new Tag keywords" provided under the view configuration. If this settings is enabled, users will not be able to create new tags while tagging an element. They can only use the existing tag.
See also
Attribute types