In digital audio, nothing can be louder than 0dB. So, if you're an ambitious engineer, and want your song to sound louder than the rest, but you still can't go above 0dB, you employ tricks to make your song apparently louder. These tricks include compression (reducing dynamic range), but more sophisticated versions like multi-band compression where different frequency ranges are compressed differently, or look-ahead limiters that sample audio ahead of the playback to limit more smoothly.
However, compression reduces dynamic range, throwing away information and resolution, and lessens fidelity.
So if I'm an engineer and want to make a recording that sounds really good, with a wide dynamic range, it's not gonna sound very loud on the radio or CD player next to the other guy's highly compressed song. That means that in order to satisfy my client and have a song that's sufficiently "loud," I've got to compress the crap out of it.
Of course, since no song can go over 0dB, that "loudness" is a subjective thing. Until now, it was difficult to come up with a way to measure it, and therefore a way to control it.
Bob Ludwig is a famous mastering engineer, and to hear that he's involved with this effort tells me it's the real deal. I own a small recording studio, and I have to deal with clients all the time that want their music louder. Maybe I'll finally have some good tools to say "This is as loud as it's gonna get."