A typical group for images types is something like print or downloads.
The image type group offers you the following settings:
Name
The internal name of this image type group.
Display Name
A display name about this image type group. This is visible in the front end. Once you have a multi language site you can enter the values for every language.
Description
A description about this image type group. This is visible in the front end.
Published
Defines if this image type group show up in the front end