Understanding Namespace
An Event Hubs namespace is a management container for event hubs (or topics, in Kafka parlance).
Container with Event Hub Namespace
Namespace provides DNS Integrated Network Endpoint which refers to the features of securing with Event Hubs : Allow access from specific IP addresses, Allow access from specific virtual networks, Allow access via private endpoints.
Specific IP addresses : https://docs.microsoft.com/en-us/azure/event-hubs/event-hubs-ip-filtering
Specific Virtual Networks : https://docs.microsoft.com/en-us/azure/event-hubs/event-hubs-service-endpoints
Private Endpoints : https://docs.microsoft.com/en-us/azure/event-hubs/private-link-service