What is Extreme Programming (XP)?
XP is the agile method with the strongest engineering opinions: pair programming, test-driven development, continuous integration, refactoring, simple design, collective code ownership, and small releases — driven by values of communication, simplicity, feedback, courage, and respect.
Where Scrum organizes the work, XP dictates how the code gets written. That's why they combine so often: Scrum's cadence, XP's craftsmanship. Exam cue: any question about pairing, TDD, or CI is XP territory.
Worked example
A trading-platform team adopts XP practices inside its sprints: all production code is paired, CI runs the full suite on every commit, and anyone may fix anything (collective ownership). Result after a quarter: defect escapes down 60%, and the bus factor — how many people can touch the risk engine — goes from one to five.