Policies are principles, rules, and guidelines formulated or adopted by an organization to reach its long-term goals. Policies are guiding principles about how business should be conducted, and they generally outline standards of conduct, conformity with legal responsibilities and guidelines, and consistent ways of handling situations. Policies should reflect the organization’s mission and values.
Procedures are the specific methods employed to express policies in action in day-to-day operations of the organization. It is extremely important that policies and procedures are consistent with each other. If a procedure contradicts a policy, neither the policy nor the procedure is valid. It is often suggested that procedures should be separate from policies, rather than included within policies, because procedures should be flexible and more easily changed than policies.
Processes are the way things are ordinarily done in a place of business. They may include formal procedures, but often they are the result of organizational culture and habits that have accumulated over time. They should be reviewed occasionally to determine whether they conform to the organization’s mission, philosophy, policies, and formal procedures. Sometimes organizations “drift” into doing things in a particular manner that is not the most effective or ethical way of handling the situation.

Source: https://www.wcsap.org/advocacy/program-management/new-directors/policies-procedures-plans-practices