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 will by default be in bold face with the same color as the headline.
|• Tag inheritance:||Tags use the tree structure of the outline|
|• Setting tags:||How to assign tags to a headline|
|• Tag groups:||Use one tag to search for several tags|
|• Tag searches:||Searching for combinations of tags|