What is the difference between a policy, a standard, a procedure, and a guideline?

A policy is a high-level statement of management intent and direction that is mandatory, such as "all data must be classified." A standard specifies mandatory requirements for implementing a policy, such as "passwords must be at least 12 characters." A procedure is a detailed step-by-step instruction for performing a specific task, such as "how to request access to the financial system." A guideline is a recommendation or best practice that is not mandatory, such as "consider using a password manager." Policies are the broadest and most authoritative.