Scrum is an iterative and incremental agile software development framework for managing product development. It defines "a flexible, holistic product development strategy where a development team works as a unit to reach a common goal", challenges assumptions of the "traditional, sequential approach" to product development, and enables teams to self-organize by encouraging physical co-location or close online collaboration of all team members, as well as daily face-to-face communication among all team members and disciplines involved.
A key principle of Scrum is its recognition that during product development, the customers can change their minds about what they want and need (often called requirements volatility), and that unpredicted challenges cannot be easily addressed in a traditional predictive or planned manner. As such, Scrum adopts an evidence-based empirical approach—accepting that the problem cannot be fully understood or defined, focusing instead on maximizing the team's ability to deliver quickly, to respond to emerging requirements and to adapt to evolving technologies and changes in market conditions.
Hirotaka Takeuchi and Ikujiro Nonaka introduced the word 'scrum' as a term in the context of product development in 1986 in their article on the New New Product Development Game. Takeuchi and Nonaka later argued in The Knowledge Creating Company that it is a form of "organizational knowledge creation, [...] especially good at bringing about innovation continuously, incrementally and spirally".
The authors described a new approach to commercial product-development that would increase speed and flexibility, based on case studies from manufacturing firms in the automotive, photocopier and printer industries. They called this the holistic or rugby approach, as the whole process is performed by one cross-functional team across multiple overlapping phases, where the team "tries to go the distance as a unit, passing the ball back and forth". (In rugby football, a scrum refers to a tight-packed formation of players with their heads down who attempt to gain possession of the ball.)