What are Restricted Groups in ADS.?

Tigermatt is this option only for this purpose or is there any other purpose we can use the restricted groups for.

You can use it for any purpose where you need to control the local groups on a domain machine. It could be used in many other scenarios too, another example I can think of is if you have a custom group which needs to be a member of the Power Users group on some servers. Since its GPO, you can use filtering and link them with OUs to control which machines should get the settings and which ones don't.

The purpose I specified is just one common example of its use.

Thanks