did u know???, page-14

re: voip FAQ
http://www.engin.com.au/public/tFAQ.asp#q18

Is engin the same as Skype?

No, engin has an Australian owned and operated telecommunications network whereas Skype utilises peoples computers and bandwidth to support phone calls that others make. engin customers are issued with a regular telephone number so that they can make and receive calls as they normally would using their existing telephone handset. Skype on the other hand relies on a Softphone based application, whereby you need to use a headset and talk through your computer.
.......

i.e. Engin you make and receive calls just like you normally would
Skype - you need to make sure your computer is on at all times to receive and make calls!