This document summarizes a seminar about GNU/Linux and open source software. It discusses: 1) What GNU is and its history and philosophy of freedom started by Richard Stallman in the 1980s. 2) How Linux was started by Linus Torvalds in 1991 and combined with GNU to create the GNU/Linux operating system. 3) Some key advantages of GNU/Linux like low cost, stability, performance, flexibility and security compared to proprietary operating systems.