Definition
Agile is less a fixed methodology than a set of values for delivering software under uncertainty. It favors working software, frequent collaboration with users, and the willingness to change direction over heavy upfront planning and contract-style specifications.
The core insight is that requirements are discovered, not dictated. Rather than predicting the whole project at the start, teams build a small slice, show it to users, learn what was wrong, and steer. Each loop reduces uncertainty.
Why it matters
How it works
A team picks a small, valuable increment and delivers it end to end within a short, fixed period. They then review what they built with stakeholders, reflect on how the work went, and adjust both the product and the process before the next increment.
Practices such as continuous integration, automated testing, and frequent releases exist to keep that loop fast and safe. The Pragmatic Programmer authors stress that agility is the goal and ceremonies are merely tools: a team can follow every ritual and still be rigid if it does not actually inspect and adapt.