Communication has always been with us ever since the origin of human society. Communication has been playing an increasingly important role especially since human society entered the information era in the 1970s or 1980s. The communication mentioned in this note refers to the communication implemented through a data communication network. This note describes the concepts related to communication and a data communication network, information transfer process, network devices and their functions, network types, and typical networking. In addition, this note briefly introduces the concepts related to network engineering and network engineers.