What are the main types of communication used in a business environment?

There are two types of business communication in an organization known as Internal communication and External Communication
Firstly, Internal Communication
Internal Communication is a type of business communication within an organization. It may be informal, formal function, or department providing communication in various forms to employees.
Under Internal Business communication, there are two division collectively known as Vertical Communication (Upward communication and Downward Communication.

Upward communication is the flow of information from subordinates to superiors, or from employees to management. While Downward Communication is an Information flowing from the top of the organizational management hierarchy and telling people in the organization what is important (mission) and what is valued (policies).
Secondly, External Communication
External Communication is an essential type of business communication which enables interaction with people outside the company