How Prestashop handles the table images in preference => images within the core

[ballashop]

hi to the whole community,
I wanted to ask for clarifications, how Prestashop 1.6 core manages the insertion of images in the structure.
An example:

cart_default
small_default
medium_default
home_default
large_default
thickbox_default
category_default
scene_default
m_scene_default

Are these name keys in the prestashop core?
Can they be modified or not?
If I create a new one, what happens?
Can you suggest me a link to more information about it?

Thanks for any reply