A better way of building software
Scrum is a management and control process that cuts through complexity to focus on building software that meets business needs. Management and teams are able to get their hands around the requirements and technologies, never let go, and deliver working software, incrementally and empirically.
Scrum itself is a simple framework for effective team collaboration on complex software projects. Ken Schwaber and Jeff Sutherland have written The Scrum Guide to explain Scrum clearly and succinctly.