There are many different ways to VoIP.
Learn the basics at: cqVoIPCall - www.cqvoip.info

There are VoIP service providers that are very versitile as to how you
access the VoIP networks. You can access using PC, VoIP ATA phone
adapters, or using Calling Card access gateway numbers using regular
phone or mobile. Learn how to roll your own customized VoIP calling
cards at:
www.cqvoip.com