Skype allows calls to be made to landlines, other VoIP users, and mobile phones. Calls to other Skype users are free, while calls to mobile phones and landlines are charged via bundle plans or pay-per-use rates. Skype uses its own proprietary protocol, which competes with SIP and H.323-based protocols used by other voice over IP apps.
The Skype brand was first acquired by eBay on September 12, 2005 for $2.6 billion USD. Microsoft purchased Skype in 2011 for $8.5 billion USD.
Skype’s first major new feature in a long time — video messaging — began internal testing in February 2013 before being officially rolled out to all platforms except Windows Phone on June 17, 2013, though users on Windows Phone can still receive and view these messages.
Skype is currently the most widely used VoIP service in the world by a large margin, with more than 70 million downloads of the application occurring on the Android OS alone as of June 2012. Microsoft merged Skype with its Windows Live Messenger service everywhere except mainland China on April 8th, giving Skype a user base of roughly 350 million, though the company hasn’t publicly released its user count in some time. The company has, however, revealed a goal to hit 1 billion total users.