From the CDC:
Policy is a law, regulation, procedure, administrative action, incentive, or voluntary practice of governments and other institutions. Policy decisions are frequently reflected in resource allocations. Health can be influenced by policies in many different sectors. For example, transportation policies can encourage physical activity (pedestrian- and bicycle-friendly community design); policies in schools can improve the nutritional content of school meals.
From the AACN (Essential V):
"Health care policy - whether it is created through governmental actions, institutional decision making, or organizational standards - creates a framework that can facilitate or impede the delivery of health care services or the ability of the provider to engage in practice to address health care needs. Thus, engagement in the process of policy development is central to creating a health care system that meets the needs of its constituents."