A policy is a high-level document/statement that is required by all management system standards. It is the top-management level document of the MS, which needs to be prepared and approved by top management to define its overall intentions and directions regarding Quality (ISO 9001), Environment (ISO 14001) etc.
A procedure is a specified way to carry out a process or an activity, that may be documented or not. Take purchasing, for example, it comprises a series of activities: selecting, evaluating, and approving suppliers, raising purchase orders, and verifying that the received goods or services meet requirements. The key personnel will need to know how to go about performing the tasks and any points of authorisation. They might be briefed on this and/or given a document to follow.
For more information on policy v’s procedure see our blog.