There are lots of resources available online to learn about Free and Open Source Software.

If you want to understand the essence and ideals of this movement, a great start would be to read the following 4 books. After reading these, you will have a good grasp of the history and philosophy of freedom in the technology world.

• Free as in Freedom: Richard Stallman's Crusade for Free Software (full text online)
• Free Software, Free Society: Selected Essays of Richard M. Stallman (full text online)
• Open Sources: Voices from the Open Source Revolution (full text online)
• Hackers: Heroes of the Computer Revolution