Open source software is computer software that is made available to the public with its source code. This means anyone can view, modify, and distribute the software freely. The collaborative nature of open source encourages innovation and allows developers to improve the software over time. Many popular programs, such as Linux and Mozilla Firefox, are open source. This approach fosters a community of users and developers who contribute to the software's development, ensuring it remains secure and up-to-date. Open source software is often seen as a cost-effective alternative to proprietary software, which requires purchasing licenses.