In the simplest terms, you're still talking about a disc and a laser for storage, but instead of reading pits in a mylar or similar surface (the way CDs and DVDs work now) the laser would be reading some sort of holographic data burned to the disc. This is a big deal because it will increase storage densities. A single holographic disk (using the tech announced here) will net you about 300 gigs, which is as big as many hard drives. The next size increase would be 800 gigs, then 1.6 terabytes. On a single disk.

So this means you could, in theory, back up your entire hard drive on a single optical disk. Not right away, of course, since the tech is going to be prohibitively expensive for a while, but that was true when the first CD burners and DVD burners came along.

The important thing is that this tech will be shipping, and the price only goes down from there. Very exciting stuff.