This document summarizes key concepts about data communication including:
1) Data flow can occur in three ways - simplex, half duplex, and full duplex. Simplex allows transmission in one direction, half duplex allows transmission in both directions but not simultaneously, and full duplex allows simultaneous transmission in both directions.
2) There are two types of signals - analog and digital. An analog signal represents information as a continuously variable physical quantity while a digital signal represents information using discrete values.
3) An intranet is a private computer network that allows information and system sharing within an organization, while the Internet is the global network of billions of computers that connects people worldwide.
