Extreme Programming (XP) is an Agile software development methodology that emphasizes flexibility, collaboration, and rapid delivery of high-quality software. It was developed by Kent Beck in the late 1990s as a response to the challenges and inefficiencies of traditional software development processes.

XP aims to reduce risk and improve the efficiency and quality of software development by focusing on customer satisfaction, constant communication, and iterative improvement.

XP is built on five core values:

1. Communication: Effective communication between team members and with customers is crucial for understanding requirements, addressing issues, and ensuring that the software meets the needs of its users.
2. Simplicity: XP promotes designing the simplest solution possible to meet the current requirements, which makes the system easier to understand, maintain, and modify.
3. Feedback: Regular feedback from customers, as well as continuous testing and integration, helps teams identify issues, adjust their approach, and improve the software incrementally.
4. Courage: XP encourages developers to embrace change, take risks, and make bold decisions, knowing that they can rely on the support of their team and the robustness of the XP practices.
5. Respect: Team members should respect each other’s skills, contributions, and opinions, fostering an environment of collaboration and trust.

Key practices in Extreme Programming include:

1. Pair programming: Developers work together in pairs, with one person writing the code while the other reviews it. This practice helps catch errors early, encourages knowledge sharing, and improves overall code quality.
2. Test-driven development (TDD): Developers write automated tests before writing the actual code, ensuring that the code meets the desired functionality and reduces the likelihood of defects.
3. Continuous integration: Code is frequently integrated and tested, making it easier to identify and fix issues early in the development process.
4. Refactoring: The codebase is continuously improved by restructuring and optimizing it without changing its external behavior. This keeps the code clean, maintainable, and efficient.
5. Small releases: Software is developed and released in small, incremental updates, allowing for rapid feedback and adaptation to changing requirements.
6. On-site customer: The customer or a representative is actively involved in the development process, providing feedback and clarifying requirements as needed.

Extreme Programming’s focus on collaboration, adaptability, and rapid delivery makes it an effective Agile methodology for teams that want to improve their software development processes and deliver high-quality products quickly and efficiently.