When creating a compartment, you must provide a name for it (maximum 100 characters, including letters, numbers, periods, hyphens, and underscores) that is unique within its parent compartment. You must also provide a description, which is a non-unique, changeable description for the compartment, from 1 through 400 characters.
After creating a compartment, you need to write at least one policy for it, otherwise no one can access it (except administrators or users who have permissions set at the tenancy level). When creating a compartment inside another compartment, the compartment inherits access permissions from compartments higher up its hierarchy.
When you create an access policy, you need to specify which compartment to attach it to. This controls who can later modify or delete the policy. Depending on how you've designed your compartment hierarchy, you might attach it to the tenancy, a parent, or to the specific compartment itself.