"Secrets" are quests and specific syntaxes in areas. By not sharing this information on public lines, it enables players who would prefer to explore on their own to do so without being spoiled.
Secrets should not be shared on public lines. While the staff finds the mud more enjoyable when discovering secrets on your own, it is understood that players will talk regardless of what policy is in place. The staff only asks that players apply some discretion when sharing with others.