6D review misses a couple things

Can you explain a bit more about this please? Can I use any camera? Do the photos have to be "bracketed" in the camera or can I use any RAW files? Is it possible to do this in Lightroom? I remember someone showing it in Photoshop and then editing in Lightroom, because it wasn't possible in Lightroom back then. Since I use both Nikon and Canon, is there a free program to do that (unless Lightroom does it)? How to do it in DPP?

This is assuming I know what bracketed photos are...