I think the reason you are not getting a response is that the definition of each is too wide. But, briefly:
A system image is an exact copy of a drive/partition, in its existing state.. By default, a system image includes the drives required for Windows to run. It also includes Windows and your system settings, programs, and files. You can use a system image to restore the entire contents of your computer, with your installed programs, to its last succesful state. If your hard disk or computer ever stops working, due to a software or virus malfunction, you use the image to replace the entire contents. It's a complete restoration - all of your current programs, system settings, and files are replaced with the contents of the system image.
A repair disk tries to fix an existing Windows installation.I system restore disk is usually something that will restore your system. But here the definition will depend on how the repair disk was made, and what is its intended repair purpose.It is normally back to the state when the system was delivered. It is normally provided, as a CD, with the system/computer on purchase, or, often, you are advised to create it the first time you boot the system.It will not, naturally, replace all the files and customisation you have subsequently installed.