The version notes feature is a feature that allows your consumers to easily view a list of changes that your API has undergone. When you create a portal and start adding your APIs to that portal, we remember changes you make to your API and create an API Version Notes section that you can view.
These notes contain some very interesting and useful information such as "breaking changes". Because we know what your API looked like before you updated it we can detect breaking changes in your API, fields that you have added, and much more. Additionally, we notify everyone following your API and all of the contributors of the API that the API was updated along with the latest version notes and any breaking changes. This is a very useful aspect of the API portal system as it keeps your consumers informed as to what they will need to change with your latest API update.