Nearly all of the software that comes with a Linux system is free software. You are free to make copies of the programs for yourself. You are free to share copies with others. You are free to change the programs (if you have the skill) and give away the modified versions. Implicit in these statements is that you get the source code to the programs.
It is possible to build an entire Linux system from scratch using the source. However, it requires a great deal of work, more than most people want to do. To make Linux systems easier to install, various groups and companies have pre-built and tested complete systems which can be obtained on CD. These are called distributions.
Although the software is free, many people find it quite reasonable to pay real money for Linux distributions--to obtain the convenience they provide. Many distributions are also available for no cost. Some of the most popular Linux distributions are:
Slackware Linux: The grandfather of Linux distributions. If you meet someone who has been using Linux for a long time, they started with this.
Red Hat Linux: The most recognized commercial name in Linux. Several ITS servers run Red Hat; including the CourseInfo server, xenon, and gold.
Debian GNU/Linux: Maintained by hundreds of volunteers, Debian is the ``most free'' of the Linux distributions. Many MTCS servers run this, including kronos.
Mandrake Linux: A commercially produced Linux; from France. It claims a very polished install and relative ease for beginners.
SuSE Linux: A commercially produced Linux; from Germany. SuSE is very popular in Europe.
turbolinux: A commercially produced Linux. The most popular Linux in Asia.