Linux (/ˈlɪnʊks/ LIN-uuks)[11] is a family of open-source Unix-like operating systems based on the Linux kernel,[12] an operating system kernel first released on September 17, 1991, by Linus Torvalds.[13][14][15] Linux is typically packaged as a Linux distribution (distro), which includes the kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses and recommends the name "GNU/Linux" to emphasize the use and importance of GNU software in many distributions, causing some controversy.[