Item notes are available in item info and bulk update. They allow you to write down comments for each SKU, like reminders, context or heads-up to their items transparent to all users, across the system.
This could be particularly interesting in some different situations, such as how sales and procurement can work together or giving information about stock out or when the stock is back, for sales to inform customers. Sales could share their estimates on how they expect new products to start selling, so buyers can buy as accurately as possible.
Item notes will not be attached to a specific user or a date stamp. All users have access to this field and all users can make adjustments.
The item notes are also available in the reports and order tabs.
You can have more information about that here.