Vertical communication in an organization is communication that flows up and down through the organization's hierarchical structure, from the general workforce up through middle management and higher management and back down again. It is the opposite of horizontal communication.
Horizontal communication is communication that flows across the same level of the organizational structure, such as departments that are on the same level in the hierarchy.
The advantage of vertical communication is that it is easier to stay in control of the company and maintain a better cohesiveness. Essentially, it allows management to control what information is disseminated throughout the company. However, horizontal communication can make it easier for more than one department to work on the same products or campaigns.