An open-source project is a software development initiative that follows the principles of open-source software. This means that the project's source code is made available to the public, allowing anyone to view, use, modify, and distribute it freely. Open-source projects are typically developed collaboratively by a community of volunteers or contributors from around the world.

Key characteristics of an open-source project include:

1. Open Access to Source Code: The project's source code is accessible and can be viewed, downloaded, and modified by anyone. This transparency fosters collaboration and encourages peer review of the code.

2. Permissive Licensing: Open-source projects are usually distributed under licenses that grant users the right to use, modify, and distribute the software without imposing excessive restrictions. Common open-source licenses include the GNU General Public License (GPL), MIT License, Apache License, and BSD License.

3. Community Collaboration: Open-source projects often have a diverse community of contributors who voluntarily dedicate their time and skills to improve the software. Collaboration typically occurs through code contributions, bug reporting, documentation, and discussions.

4. Transparency and Accountability: Since the source code is accessible to the public, any potential issues or security vulnerabilities can be identified and addressed by the community. This fosters a sense of accountability and promotes software quality.

5. Iterative Development: Open-source projects usually evolve through an iterative process, where new features, bug fixes, and improvements are continually integrated into the codebase. The community reviews and approves changes through various mechanisms like pull requests and code reviews.

6. Freedom of Use: Users are free to install, run, and deploy open-source software for any purpose without facing licensing fees or restrictions.

7. Community Support: Many open-source projects have vibrant communities that provide support through forums, mailing lists, chat platforms, and documentation, making it easier for users and contributors to seek help and guidance.

Some well-known examples of open-source projects include the Linux operating system, the Apache HTTP Server, the Python programming language, the WordPress content management system, and the Mozilla Firefox web browser. These projects have achieved widespread success and popularity due to the collaborative efforts of the open-source community.