When you see the phrase Free Software spelled like that with initial capital letters, it has a special meaning. The small games or zipping programs or other tid-bits that you can sometimes download for free from the internet or perhaps get for free on a DVD that comes with a computer magazine do not qualify to be called Free Software. They are merely freeware. Free Software is a greater concept, and it also has implications that relate to you and how safe you can make your computing experience.
Free Software was first conceived by the great programmer and social activist Richard Stallman in 1985, and from the very beginning it has been designed to fight the evil system of making a program's internal operation unavailable to other people. Stallman and his collaborators wrote a special software license agreement called the GNU Public License (GPL for short). This has had far-reaching consequences for the software world ever since.
Any software distributed under the GPL must make its source code available to the recipient. A program's source code is its actual programming, written in text form in some computer language, which any programmer can see and understand what the program is trying to do and why. The usual programs we use every day, like the Windows Operating System, or the games we play on it, or the office suites and other programs that we usually run are all closed-source software. Which means that their source code is secret, and no one but the distributing company knows how it really does what it does.
Freeware is merely closed source software that is distributed for free. But Free Software is a program that is distributed under the terms of the GPL, and the source code is provided with it. What is more, if you are a programmer, you can modify or re-write GPL-ed software freely, provided when you redistribute your modified program, you give the same modification and redistribution rights to the recipients. In this way Free Software tries to create a never-ending cycle of freedom, in an effort to break free from the clutches of monopolistic closed-source software vendors.
Why should you use free software? Well, apart from the issue of social commitment and political choice, Free Software is also exceptionally robust and free of security holes. This is possible because the source code is freely available to everyone, so there is no chance that a malicious code can hide inside the program. There is no 'inside' of the program, so to speak.
Further, popular examples of Free Software are reviewed by so many thousands of top-notch programmers worldwide that errors and bugs get fixed almost as soon as they are discovered. Most of the programs that run on Linux, and also the Linux kernel itself, are Free Software. You can see for yourself what wonders this kind of peer-review has done for Linux security. The Windows world is riddled with viruses, trojans, spyware and other security threats. There is not a single successful virus for Linux yet.
So if you are concerned about online security for your computer, opt for Free Software. You can find an extensive list of Free Software here.