-"Voice over Internet Protocol [VOIP] is the technology used to transmit voice conversations over a data network using the Internet Protocol. Such data network may be the Internet or a corporate Intranet." Basically, it's a free telephone within your computer.
-Online telephony is probably my favorite web feature of the past few years because it is so clearly on the verge of redefining the telephone industry to the benefit of the consumer.
-In addition to regular telephony most services (i.e. Skype) allow you to use video conferencing, text chat as well as collaborative workspaces where you can upload documents, spreadsheets, images and draw on virtual whiteboards.
-Online Telephony Services