QPID / AMQP Messaging
QPID (http://qpid.apache.org/) is a messaging bus that virt_web uses to communicate with each node. In the simplest setup the qpid service would run on the virt_web server. Each node would then contact the qpid server on port 5671 or 5672 depending on if ssl is enabled. This has several benefits, the biggest being that each node configuration is very simple. Typically just installing libvirt-qpid and altering /etc/sysconfig/libvirt-qpid is enough. No firewall changes to make on the nodes, no open ports to worry about. All communication is done from the node communicating the qpid server.
libvirt (http://libvirt.org/) is a library abstraction layer for virtualization technologies. By building on this industry standard library virt_web supports xen, qemu, kvm, LXC, OpenVZ, user mode linux, and virtual box. The internals of virt_web use the same terminology as libvirt so development and api use should be familiar to anyone who is already familiar with libvirt. Examples of this include "create" when starting an existing guest, undefine to delete guests, etc.
TurboGears (http://turbogears.org/) is a python web development framework that allows for quick development and a stable environment. This will allow virt_web to continue to mature and change as libvirt matures and changes.
Another feature of virt_web is it's rich json api. Through this api, sysadmins should be able to write scripts to completely rebuild, start, stop, mass create, mass delete or automate pretty much any task that can be done by libvirt.