VOIP is an acronym for for "Voice over Internet Protocol". More importantly (and without the jargon) VoIP
refers to a standard for voice transmissions travelling over ADSL or Broadband connections.
This standard holds the key to cheaper communications: Telephone over the Internet.
free voice calls worldwide between voice-over-ip subscribers
one number worldwide
many calls on one Internet line at the same time
voicemail by email and by phone
numbers from different countries on the same phone
What do I need to use this service
an Internet connection
a SIP compatible phone or a SIP compatible softphone