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).