These features, apart from the Change master password screen, run PostgreSQL administration commands on the server and report back through the web interface.
The master password is a very important piece of information that only lives in the Odoo server configuration file and is never stored in the database. There used to be a default value of admin, but using this value is a security liability as it is well known. In Odoo v9 and later, this is identified as an "unset" master password, and you are urged to change it when accessing the database administration interface. Even if it is stored in the configuration file under the admin_passwd entry, this is not the same as the password of the admin user; these are two independent passwords; the master password is set for an Odoo server process, which itself can handle multiple database instances, each of which has an independent admin user with his own password.
To create a new database, Odoo uses the PostgreSQL createdb utility and calls the internal Odoo function to initialize the new database in the same way as when you start Odoo on an empty database.
To duplicate a database, Odoo uses the --template option of createdb, passing the original database as an argument. This essentially duplicates the structure of the template database in the new database using internal and optimized PostgreSQL routines, which is much faster than creating a backup and restoring it (especially when using the web interface that requires downloading the backup file and uploading it again).
Backup and restore operations use the pg_dump and pg_restore utilities, respectively. When using the zip format, the backup will also include a copy of the file store that contains a copy of the documents when you configure Odoo to not keep these in the database, which is the default in 11.0. Unless you configure it otherwise, these files live in ~/.local/share/Odoo/filestore.