High-level statements of the goals, objectives, or needs of an organisation. They usually describe opportunities that an organisation wants to be realised or problems that they want to be solved. Often stated in a business case.
Mid-level statements of the needs of a particular stakeholder or group of stakeholders. They usually describe how someone wants to interact with the intended solution. Often acting as a mid-point between the high-level business requirements and more detailed solution requirements.
Usually detailed statements of capabilities or behaviour required only to enable transition from the current state of the enterprise to the desired future state, but that will thereafter no longer be required.