In its simplest form, telephony is simply a collective term for all types of voice equipment which allow communication between two points. This used to only be possible by means of analog copper wires, but due to advances in technology, this has come to also include electronic or digital transmission of voice between locations.
Almost everyone is impacted by telephony on a daily basis. The star of the telephony show is the telephone itself, which is considered an essential in just about every residence and in all businesses. The telephone provides basic point to point audio communication that we depend on every day.
As telecommunications equipment and solutions continue to evolve, however, telephony equipment will also continue to change with the times and redefine the nature of how we communicate with one another. This is seen clearly by impact that cellular transmission and computers have had on voice communication.
Ever since computers arrived on the scene and enabled us to transmit digital information over telephone systems, the words telephony and telecommunication have become almost synonymous. Now, telephony encompasses traditional PBX phone systems as well as offsite hosted business phone systems such as VoIP and Cloud telephony deployment models. Telephony has grown into Unified Communications (UC) due to the ability to integrate phone systems with many other programs, applications, and forms of communication and collaboration.
To understand more about the history and architecture of telephony, see PSTN.