Agile software development is a conceptual framework for
software engineering that promotes development iterations
throughout the life-cycle of the project.

There are many agile development methods; most minimize risk
by developing software in short amounts of time. Software
developed during one unit of time is referred to as an
iteration, which may last from one to four weeks. Each
iteration is an entire software project: including planning,
requirements analysis, design, coding, testing, and
documentation. An iteration may not add enough functionality
to warrant releasing the product to market but the goal is
to have an available release (without bugs) at the end of
each iteration. At the end of each iteration, the team
re-evaluates project priorities.