Increased / Enhanced Nitrogen Retention what does that mean for us?

We hear about it all the time but what does it mean?
Enhanced Nitrogen Retention: All lean muscle tissue is comprised of approximately 16% nitrogen. As nitrogen levels fall, this can lead to a catabolic (muscle wasting) state. The more nitrogen we retain the more anabolic we remain. Again, the anabolic atmosphere is enhanced, recovery is improved and progress enjoyed.