Permission types describe a level of access to secured operations or resources, such as files or environment variables. Permission instances do not confer the right to access a resource or perform an operation; the security system determines whether or not requested permissions are granted. Permissions are used by both application code and the security system in the following ways:

• Code requests the permissions it needs in order to run.
• Permissions are granted by the security system.
• Code demands that calling code has a permission.
• Code alters the default behavior of the security system by asserting or denying permissions.