I have a habit of buying braising steak, when intending to stew some beef (be it to eat as a stew, or to later use as a pie filling), but I've always wondered what braising actually is?
From The Professional Chef:
To braise meat, first sear it in hot fat to the desired color, then simmer it in a covered vessel in stock or another cooking liquid. The amount of liquid used in the braise is crucial to the success of the finished dish.
One of the benefits of braising is that tough cuts of meat become tender as the moist heat gently penetrates the meat and causes the connective tissues to soften. Another benefit is that flavor is released into the cooking liquid to become the accompanying sauce, thus virtually all of the flavor and nutrients are retained."
Braising is a combination of fast dry heat and long slow moist heat.
The fast dry heat is able to create the flavorful crust on meat in ways that slow heat can't. The dry heat can be extremely hot air in the oven, direct radiation from a broiler, or contact with a hot steel or cast iron pan.
The long slow moist heat creates a steaming process. Importantly, the meat is NOT submerged and boiled in the liquid. The long heat helps break down the tough connective tissue, and the steam helps the meat not dry out. The steam, rather than immersion means more flavor stays with the pieces of meat instead of leeching out into the broth like a stew.
Braising is best used for meat that is too tough to use as good steak, but good for more than just becoming stew meat.