Skype is a telecommunications application software product that specializes in providing video chat and voice calls between computers, tablets, mobile devices, the Xbox One console, and smartwatches via the Internet and to regular telephones. It is one of the more popular methods of making voice calls (emulating telephones) over the Internet.
Microsoft purchased Skype from a privately-owned company in May 2011 for $8.5 billion. At the time, Skype was very popular, primarily because of its high audio quality and ease of use. Skype also was believed to be very secure at the time. While never officially stated, the advertising for Skype hinted that conversations between two Skype users (not traveling over public telephone lines) could not be wiretapped in its distributed, peer-to-peer network.
In the years since the acquisition, the ease of use in Skype has gone away, replaced by a very awkward user interface that is obviously designed for corporate use. The audio quality remains rather good. The original peer-to-peer network has been replaced with a more-or-less standard network that uses Microsoft servers to establish connections. The new network appears to be less secure than the previous peer-to-peer implementation.