A multisite network is a collection of websites that all share the same WordPress installation. They can also share plugins and themes. The individual sites in the multisite network are virtual websites in the sense that they do not have their own directories on your server, although they do have separate directories for media uploads within the shared installation, and they do have separate tables in the database.
You can use subdomains or subfolders for multisite.
To enable the Network setup menu item, just need t add below one line code in wp-config.php.
/* Multisite */ define( 'WP_ALLOW_MULTISITE', true );
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