It is software that stimulates the functioning of a telephone and allows you to make, receive and manage voice calls over the Internet (http://voip.about.com/od/glossary/g /SoftphoneDef.htm) . This software is very common and is typically already installed on computers, tablets and smartphones. They contain an interface that serves as a communication platform between users and the device. There is also a call processing engine. This allows you to make and receive calls. Codecs allow you to encode voice data between analogue. This makes it easier to transfer over the Internet. Finally, there is a contact list that helps you keep track of numbers and