This is the official manual for the latest Org-mode release.
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.
You may specify special faces for specific tags using the option
org-tag-faces, in much the same way as you can for TODO keywords
(see Faces for TODO keywords).