According to the PMBOK® Guide, effective communication requires the project manager to recognize and manage the different dimensions of communication to ensure the right information reaches the right person.

Formal Communication: This involves structured and documented information. It is essential for maintaining the project ' s " official record. "

Focus: Reports, meeting agendas, and minutes. These are formal artifacts that may be used for audits or legal documentation.

Internal Communication: This refers to communication within the project and the performing organization.

Focus: Project stakeholders. While customers are stakeholders, in this specific categorization, " Internal " refers to the team, senior management, and functional departments within the company.

Informal Communication: This involves less structured, daily interactions that help build relationships and solve minor issues quickly.

Focus: General communications activities using email. While email can be formal, general daily emails, ad-hoc conversations, and social media activities are classified as informal dimensions.

External Communication: This refers to communication with entities outside the performing organization.

Focus: Customers and vendors. Since these parties are outside the legal boundary of the company, communication with them often requires specific protocols (contracts, formal statements, or specialized account management).

Internal vs. External: The key differentiator is the organizational boundary. Employees and internal managers are internal; anyone else (contractors, government regulators, clients) is external.

Formal vs. Informal: The key differentiator is the level of structure and permanence. If it belongs in the project archives as a record of a decision, it is formal. If it is a tool for coordination and team bonding, it is likely informal.