Skype is a peer-to-peer Internet telephony service that is free for Skype-to-Skype calls. The service also allows Skype users to call mobiles and landlines, and vice-versa. Skype has special charge plans for non-Skype-to-Skype calls. Skype is expanding from its traditional computer-based calls to mobile applications.
Skype was founded by Niklas Zennstrom and Janus Friis who were also the founders of the file sharing application Kazaa and the peer-to-peer television application Joost. Skype is different than other VoIP services in that it uses a peer-to-peer model instead of a server-client model. Its main competitors include GizmoProject, PeerMe and Jajah.