The full form of PBX is Private Branch Exchange. It’s used on Technology ,Communication in Worldwide

A private branch exchange (PBX) is a telephone exchange that serves a particular business or office, as opposed to one that a common carrier or telephone company operates for many businesses or for the general public. PBXs are also referred to as PABX – private automatic branch exchange

A traditional PBX system is made up of standard telephone lines and stations, which allows it to make connections to the PSTN through endpoint devices like telephones or fax machines. With a traditional PBX, an organisation is constrained to a maximum number of outside telephone lines and a maximum number of internal devices and extensions.

An IP PBX (Internet Protocol Private Branch Exchange) is a PBX system with IP connectivity that provides additional communication features like audio, video and instant messaging. An IP PBX allows for an unlimited number of extensions and lines as well as complex functions that are difficult to implement with a traditional PBX. To sum it up, an IP PBX adds IP VoIP support to the older PBX system.