What is Free Software?

  1. Freedom 0: Freedom to use the program for any purpose,
  2. Freedom 1: Freedom to study the program and learn from it,
  3. Freedom 2: Freedom to redistribute the program and share it with others, and
  4. Freedom 3: Freedom to make changes to the program and resdistribute this modified version.

Further reading: https://www.gnu.org/philosophy/free-sw.en.html