It is a method of communication based on text messaging between two fax machines, the first one calling to other one to send a fax, the recipient receives a text on A4 paper and after that communication process ends.
Virtual PBX or Hosted PBX is offered by a telephone company and can free your business from investing in the costly hardware or a complex business phone system. Virtual PBX means that every service is processed via a telephone company offering a service with their own hardware and software.