An excellent way to implement labels and contexts for cross-correlating information is to assign tags to headlines. Org mode has extensive support for tags.
Every headline can contain a list of tags; they occur at the end of
the headline. Tags are normal words containing letters, numbers, ‘_’,
and ‘@’. Tags must be preceded and followed by a single colon, e.g.,
‘:work:’. Several tags can be specified, as in ‘:work:urgent:’. Tags
by default are in bold face with the same color as the headline. You
may specify special faces for specific tags using the variable
org-tag-faces, in much the same way as you can for TODO keywords
(see Faces for TODO keywords).
|• Tag Inheritance:||Tags use the tree structure of an outline.|
|• Setting Tags:||How to assign tags to a headline.|
|• Tag Hierarchy:||Create a hierarchy of tags.|
|• Tag Searches:||Searching for combinations of tags.|