What is XBMCbuntu?

I have an ASUS EB1501 (1.6 GHz Atom with NVIDIA ION graphics card) running Win7 32-bit.

I installed V12 "Frodo", but I'm now looking at XBMCbuntu on the download page noticing where it shows "AMD - Intel/NVIDIA" under its icon.

All that is inside it are ISO files, though.

What is this? Is it a Linux OS with XBMC integrated into it or something I would install on top of Windows?