Cgroup or Control Groups, in Kubernetes, are increasingly used for limiting the resources like CPU, and memory. And thus, cgroups do not isolate resources, rather they put limits to the resources and thus ensures that an application is not starving of other applications in cgroup.
If you are aiming for a career in Kubernetes, check out the Kubernetes course from Intellipaat. And if you wish to get your fundamentals clear in Kubernetes, check out Fleet Management for Kubernetes.