The acronym "PBX" stands for Private Branch Exchange in telecommunications. PBX is a telephone system that connects internal phones within an organization to the outside public telephone network. It enables features like call routing, voicemail, and conference calling, streamlining communication for businesses. By handling internal and external calls efficiently, PBX systems improve operational efficiency and reduce costs, as organizations can manage their telephone traffic without relying solely on external telephone lines. Modern PBX solutions can be hardware-based or cloud-based, offering flexibility and scalability.