PBX stands for Private Branch Exchange. It’s a private telephone network that a business or organisation uses for internal communication. When you pick up your desk phone and press a button or punch in an extension to speak to someone elsewhere in the building, you’re using a PBX. Hosted PBX, which can also be described as either cloud PBX or virtual PBX, is a more modern version of the system. 

It moves the functions of onsite PBX hardware to the cloud. Instead of connecting telephones to an on-premise PBX, a hosted PBX system connects them to secure data centres. That lets users dial out and receive calls via VoIP. You get all the features of an on-premise PBX—and more—delivered seamlessly to desk phones, computers, and even mobile devices.