Firefox OS (project name: Boot to Gecko, also known as B2G) is a Linux-based open-source operating system for smartphones and tablet computers and is set to be used on smart TVs. It is being developed by Mozilla, the non-profit organization best known for the Firefox web browser.
Firefox OS was publicly demonstrated in February 2012, on Android-compatible smartphones, and again in 2013 running on Raspberry Pi. In January 2013, at CES 2013, ZTE confirmed they would be shipping a smartphone with Firefox OS, and on July 2, 2013, Telefónica launched the first commercial Firefox OS based phone, ZTE Open, in Spain which was quickly followed by GeeksPhone's Peak+.
source : wikipedia