Tags make use of the hierarchical structure of outline trees. If a heading has a certain tag, all subheadings will inherit the tag as well. For example, in the list
* Meeting with the French group :work: ** Summary by Frank :boss:notes: *** TODO Prepare slides for him :action:
the final heading will have the tags ‘:work:’, ‘:boss:’, ‘:notes:’, and ‘:action:’ even though the final heading is not explicitly marked with those tags. You can also set tags that all entries in a file should inherit just as if these tags were defined in a hypothetical level zero that surrounds the entire file. Use a line like this1:
 As with all these in-buffer settings, pressing C-c C-c activates any changes in the line.