Requirements gathering is the process of identifying your project's exact requirements from start to finish. This process occurs during the project initiation phase, but you'll continue to manage your project requirements throughout the project timeline.
What is requirements gathering in agile?
Agile requirements gathering is a practice teams often perform on the fly. For example, developers update requirements between iterations -- if the software project has documented requirements at all. Some Agile practice purists balk at the word requirements.
Why do we need requirements gathering?
Requirements gathering is an opportunity to define key performance indicators that allow you to track your achievement of business benefits. This is important for tracking benefits during implementation, determining your ROI after implementation and continuing to realize benefits for years to come.