Denotes questions regarding Magento custom attributes
Denotes questions regarding Magento custom attributes which are those added on behalf of a merchant. For example, a merchant might need to add attributes to describe products, such as shape or volume. A merchant can add these attributes on the admin panel, and these attributes can be displayed.
Extension attributes in Magento 2 are used to extend functionality and often use more complex data types than custom attributes. These attributes do not appear on the GUI.
Official documentation:
http://devdocs.magento.com/guides/v2.0/extension-dev-guide/attributes.html http://devdocs.magento.com/guides/v2.1/extension-dev-guide/attributes.html http://devdocs.magento.com/guides/v2.2/extension-dev-guide/attributes.html
