Ironic is an OpenStack project which provisions bare metal (as opposed to virtual) machines by leveraging common technologies such as PXE boot and IPMI to cover a wide range of hardware, while supporting pluggable drivers to allow vendor-specific functionality to be added.
If one thinks of traditional hypervisor functionality (eg, creating a VM, enumerating virtual devices, managing the power state, loading an OS onto the VM, and so on), then Ironic may be thought of as a hypervisor API gluing together multiple drivers, each of which implement some portion of that functionality with respect to physical hardware.
The documentation provided here is continually kept up-to-date based on the latest code, and may not represent the state of the project at any specific prior release.
For information on any current or prior version of Ironic, see the release notes.