Free software, also known as software libre, or open source software, is a type of software that can be used and modified by the software owner, as well as redistributed. Often, it may be redistributed and sold by the person who has done the modifications, but it still needs to remain open source. Free software is not synonymous with "freeware," which is software that is available for use free of charge, but may or may not be modified. This software is sometimes also free of charge, but sometimes requires a fee to purchase; the "free" in the name refers to the fact that it may be freely used and changed.
This type of software may also be referred to as open source software. All of these terms mean the same thing, and simply refer to the fact that the source code of the software is available to each person who has the software on his or her computer. The source code of the software should remain available in both the original version and any modified versions; if it is not, then the software can no longer be considered free. Of course, people are free to make their own personal changes to the software and not share it with anyone. Just because the freedom to do so exists does not mean it is required.
Free software may be software of any type, and may be used by anyone who wishes to install the software on his or her computer. The Free Software Foundation was first developed in 1985 by Richard Stallman, and provides a list of four specific "freedoms" that help to simplify the definition of free software. These are "The freedom to run the program for any purpose," "the freedom to study how the program works, and change it to make it do what you wish," "the freedom to redistribute copies so you can help your neighbor," and "the freedom to improve the program, and release your improvements (and modified versions in general) to the public, so that the whole community benefits."
In addition to the source code for the free software being available to the public, the software must also be accompanied by either a free software license or another notice that provides additional permissions. A manual is usually included with the software as well, which is also typically updated by users who make modifications. This type of software can be beneficial for individuals as well as larger groups or corporations, because the software can continuously be improved and customized based on the users' needs.