OpenStack Networking is the Software Defined Networking (SDN) component of OpenStack and its project name is Neutron. With SDN, we can describe complex networks in a secure multitenant environment that overcomes the issues often associated with the Flat and VLAN OpenStack networks. In OpenStack, SDN is a pluggable architecture, which means we are able to plug in and control various switches, firewalls, and load balancers and achieve various functions such as Firewall-as-a-Service. All this is defined in software to give you fine-grained control over your complete cloud infrastructure.
OpenStack Networking is a replacement for the networking component that is available with OpenStack Compute itself: nova-network. While nova-network is still seen as more robust and available for use, many people are deploying OpenStack Networking in production. Nova-network is expected to be deprecated in an upcoming release of OpenStack.