We've talked about Storage and Compute, what's left? Networking of course. A newer project called Neutron is being used instead of Nova (the compute project) to handle networking. By using Neutron we can connect actual network gear to our OpenStack Deployment. Thereby we're using ASICs and CPUs that are specifically built to forward frames and packets, thereby saving from some performance hits you may have taken on your compute and likely offering more complex networking and better performance.
This project was originally called Quantum but due to trademark rights the name had to be changed. It has been Neutron for about 3 years now. So if you hear someone accidentally say Quantum, they really mean Neutron.