What is open-source software?

Open source software is software with source code that anyone can inspect, modify, and enhance.

"Source code" is part of the software that most computer users don't ever see; it's the code computer programmers can manipulate to change how a piece of software—a "program" or "application"—works. Programmers who have access to a computer program's source code can improve that program by adding features to it or fixing parts that don't always work correctly.

There are many good descriptions and debates which are publicly available on the web, but few are more elegant than this one from OpenSource.com where they have compiled several resources designed to help understand more about open source: What is Open Source Code?