What’s known as a combination cooking method, this method of cooking uses both wet and dry heats. In effect, braising is a combination of roasting and steaming. Etymologically, the term braise can be traced back to the French word braiser. However, the process itself is far older.
Typically, the braising process starts with browning the food in question in a small amount of fat some kind. The type of fat depends upon what exactly is being braised and the flavor profile that you desire. Depending on the food in question, you may not need to add any fats at all. Alternatively, if you want a relatively lighter flavor profile, you might go with butter since that won’t sacrifice a creamy thickener in exchange for the lighter flavor. You could go with the more neutral olive oil or you could go with some beef tallow for a very rich, heavy flavor. The point is that you want to choose a fat that will compliment the dish you are making, if you add any fats at all.
Following this, the food is then simmered in a small amount of liquid, typically in some type of covered dish. Times to completion of the braising process vary, but the important thing is that the food in question is tender. You may use a wine or a stock of some kind to impart a richer flavor to the dish. Feel free to get a bit creative with this part.
As I said earlier, braising is a method that has quite the (appropriately) rich history. So much so that the braising is at least 300,000 years old as a technique. Given the time period, there isn’t anything in the way of written records, so we mostly rely upon archeological evidence for this information.
There are a few reasons why you may want to go with braising a food. For one thing, braising is a time intense technique, making it ideal for occasions when there is a lot of cooking time available to you or when long cooking times are necessary for some reason. Otherwise, the best reason to resort to braising (aside from instructions) is that the reduction process results in a thickening process that creates a nice sauce out of the fat and/or liquids used and/or released during the braising process.
Now, the last thing that I would like to add is that braising does not have to be used exclusively for meats. Sure, a lot of people have this idea of braising something like a nice, meaty pork shoulder. However, you could just as easily braise a Portabella mushroom or a head of cabbage. Again, feel free to get a bit creative with this.