Wet-aging holds beef in vacuum-sealed, cryovac packaging at a controlled cold temperature for an extended period. Over that time, natural enzymes already present in the muscle slowly break down connective tissue and muscle fibers, which is what makes the meat noticeably more tender.
It also gives the beef more time to develop flavor. Most retail beef is aged for a matter of days before it reaches the shelf. We age ours 80 to 120 days, which is long even by butcher-shop standards, and it is the biggest single reason our beef tastes different from what most people are used to.
The tradeoff is time and trim loss, which is part of why properly aged beef costs more than beef sold within a week of butchering. We think the difference in a bite is worth it.