The document discusses informal communication networks known as "grapevines" that exist within organizations. It defines grapevines as informal channels for spreading information parallel to official channels. The summary discusses how grapevines can develop for reasons like uncertainty or limited formal communication. While grapevines can spread information quickly, they may also spread partial or inaccurate information in the form of rumors. The document provides tips for managing grapevines, like providing clear information through formal channels or preventing rumors.