All of the above. Container Registries provide a central location for storing and managing Docker images and other container-based deployments. 

They also allow for easy access and deployment of containers across different environments and platforms, and provide tools for tracking and monitoring the performance and health of container-based deployments. 

https://medium.com/aspnetrun/deploy-microservices-into-cloud-azure-kubernetes-service-aks-with-using-azure-container-registry-b661698610b1