What is Activity-based Management?

Legal Definition
Activity-based management (ABM) is a method of identifying and evaluating activities that a business performs using activity-based costing to carry out a value chain analysis or a re-engineering initiative to improve strategic and operational decisions in an organization.
-- Wikipedia
Legal Definition
When management adds activities that help and removes ones that don't. It improves efficiency and market effectiveness. It tries to reduce cost, measure performance, improve cash flow, improve quality, and enhance value or a product.