From the "Purpose" section: "In support of the National Security Strategy, which sets forth national security priorities, the National Intelligence Strategy (NIS) provides the IC [Intelligence Community] with the mission direction of the Director of National Intelligence (DNI) for the next four to five years. IC activities must be consistent with, and responsive to, national security priorities and must comply with the Constitution, applicable statutes, and Congressional oversight requirements. The NIS should be read along with the National Intelligence Priorities Framework and Unifying Intelligence Strategies to inform and guide mission, as well as planning, programming, and budgeting activities." The NIS outlines organizational framework, mission, vision, and ethics for the IC.
Office of the Director of National Intelligence: http://www.dni.gov/