VoIP (voice over IP - that is, voice delivered using the Internet Protocol) is a term used in IP telephony for a set of facilities for managing the delivery of voice information using the Internet Protocol (IP). In general, this means sending voice information in digital form in discrete packets rather than in the traditional circuit-committed protocols of the public switched telephone network (PSTN). A major advantage of VoIP and Internet telephony is that it avoids the tolls charged by ordinary telephone service. 

Virtual Private Networks is A point to point secure connection through the Internet encryption. Lets say head office has an accounting application that is essential to their business, and the satellite offices are currently having to courier back and forth disks to sync the data. A vpn could let a satellite office connect directly to head office and run the application off the head office server over a secure (encrypted vpn) connection.

You could conceivably have a work group spread out over the globe, with shared drives and printers, immune to hacking, and transparent to the end users.