Private AccessPrivate Access
This function’s access is marked private. This means it is not intended for use by plugin or theme developers, only in other core functions. It is listed here for completeness.
Add additional default image sub-sizes.
These sizes are meant to enhance the way WordPress displays images on the front-end on larger, high-density devices. They make it possible to generate more suitable
sizes attributes when the users upload large images.
The sizes can be changed or removed by themes and plugins but that is not recommended. The size "names" reflect the image dimensions, so changing the sizes would be quite misleading.