OpenStack supports rich abstractions to handle virtual networking needs in a cloud. As a user the most visible entities are the Network, Subnets, Routers, Firewall etc. But if we consider ingress and egress points for data traffic, the most critical entity is the Port. OpenStack Neutron Ports are usually created automatically as part of other user operations. However the CLI allows users to create Ports independently as well.
Here is an overview of three basic networking devices - Hub, Bridge and a Switch. This blog and the related YouTube video at the end, will be useful for upcoming topics related to virtual networking such as Linux Bridge and Open vSwitch.