The Tails project is a Debian-based distribution designed to improve online privacy and security.
Much of the core technology in the Tails distribution comes from the Tor Project, so it's no surprise that the two projects decided to come together and collaborate. 
“Today the Tor Project, a global non-profit organization developing tools for online privacy and anonymity, and Tails, a mobile operating system that uses Tor to protect users from digital surveillance, joined forces and merged functions ".
“By incorporating Tails into the Tor Project structure we will have easier collaboration, better sustainability, reduced costs, and expanded training and outreach programs to address a greater number of digital threats. In short, the merger will strengthen both organizations' ability to protect people around the world from surveillance and censorship."
Details of the merger can be found at Tor Project website.
