While the first three channels of communication are formal ways, the last one is an informal way of communication.

Vertical Communication

Vertical communication can be divided into two categories i.e. upward communication and downward communication.

Downward communication refers to communication that flows from the superior authority to the subordinate authority or from the higher level to the lower level. It is the most important direction of communication and the very nature of the organisation. No organisation can function without it. Downward communication is mostly used give instructions - both written and spoken, letters, memorandum, policy matters, speeches, meeting, information etc.

Upward communication refers to communication that flows from the subordinate to the superior or from the lower level to the upper level. It is mainly used by employees to give feedback about various responsibilities and also to give suggestion about how the task was executed. It includes reports, proposals, suggestions, grievances, etc

Horizontal Communication

When communication takes place between two or more persons who are subordinates working in the same section or department, it is called as horizontal communication. It is one of the most frequently used channels of communication to maintain coordination between people of the same section or level. In this process message flows not only up and down but also sideways. During such interactions the views of each other are made known and decisions are arrived quickly. Here we find no superior or subordinate relationship.

Diagonal Communication

It includes the horizontal flow of information as well as interaction across different levels of an organisation's hierarchy. Diagonal communication is used to speed up the flow of communication. It makes effective efforts for achieving organisational goals.

Grapevine Communication

Grapevine communication is a type of informal business communications which develops within an organisation. It means gossip. Usually gossip that spreads and covers a lot of ground (a lot of people) like vines do. However there are disadvantages or limitations to grapevine communication. It has the potential to spread unnecessary  gossips.It can be dangerous to the organisation if allowed to grow without monitoring. It may result in character assassination and personal vilification of individuals. It may provoke sudden unwanted and unexpected reactions from emotionally unstable people. Grapevine channel can be moderated but not eliminated.