An ONIX feed provides standard metadata about your books to trading partners. It includes information about a book's author, publisher, price, publication date, physical dimensions, synopsis and many other details. This ONIX feed is sent from the publisher to various trading partners to create or update title information on their websites.
Eloquence, a service owned by NetGalley's parent company Firebrand Technologies, is the industry standard for ONIX distribution in the United States. For more information about the service, visit http://www.firebrandtech.com/solutions/eloquence.php.
You do not need to use ONIX to add titles to NetGalley. You can create titles in NetGalley one-at-a-time using the "Create New" button on the Manage Titles page (more info here). You can manually edit the NetGalley title record from within the NetGalley application.