A run of content that is marked or highlighted, such as for reference purposes, or to call it out as having a special purpose.
If the marked content has an associated section in the document elaborating on the reason for the mark, then
atspi_relation_details should be used on the mark to point to that associated section. In addition, the reciprocal relation
atspi_relation_details_for should be used on the associated content section to point back to the mark.
Since: 2.36.