In the purest and simplest sense, bacon is a belly of pork which has been cured by salting; but of course there are numerous regional variations of bacon; some smoked, some not, some cooked and some raw - some don't even use belly pork, but another cut entirely.
Historically, bacon was a staple food for the working class. Pigs were cheap and easy to breed for the table, as they will eat virtually anything (including cars if you believe Emir Kusturica). Bacon is always cured, or salted - a process that draws moisture out of the meat and significantly delays spoilage, so it can be kept for long periods. In addition, many styles of bacon are smoked, which combined with the fatty nature of pork belly provides bacon with a rich and hearty flavour - meaning a little went a long way to feeding the whole family.
The English word is derived from the Old French word, bakko; meaning ham. The Modern French word bacon came to mean any cut of pork, usually salted. The French even had a term repas baconique, which was a festival where only pork was served. The English perfected the technique of salt curing and smoking belly pork and borrowed the French term for the meat, and the word was returned to the French and now means what it does in English speaking countries; salted belly of pork.
The traditional preparation of bacon involves salt - and lots of it. Once the pig has been slaughtered, the belly is removed and rubbed with dry salt. The moisture that is drawn out of the pork due to simple osmosis quickly forms a brine. The belly is left to steep and cure in this salty liquid and turned daily, for up to 2 weeks. Once fully cured, the belly is washed of excess salt and then given one of three treatments - air-drying, cold-smoking or hot-smoking. The first two result in raw bacon, much in the same manner that gravlax and smoked salmon result in raw fish. Hot smoked bacon on the other hand has been cooked through.
These days most bacon found in supermarkets is hot smoked, but not in the traditional manner. The whole process is expedited (and therefore much cheaper) by first injecting the un-cured belly with brine, then an atomized smoke and hot water solution is injected to cook and provided a smoky flavour to the belly. This is bacon at its most pointless, and when prepared in such a manner it tends to ooze moisture in the pan and end up dry. The flavour also suffers, instead of a full and delicious natural smoke flavour, a pale chemical imitation is the result.
The only way to get real bacon these days is to visit specialist butchers that prepare their own. Not only will you receive a superior product, but you will be supporting a dying art that if we are not careful, will disappear forever. German and Austrian butchers make a product called kaiserfleisch or sometimes speck, and good Italian butchers will make pancetta. These are both prepared in a very similar manner to good quality bacon. Of course, you could try visiting a specialist English or Irish butcher and ask for raw or green bacon, which ideally should be cold smoked.
Bacon is not made form the same pigs you get regular pork from. Table pork is produced form 3 different grades of pigs; porkers, superporkers and finishers. These tend to have lean meat and a dressed weight of up to 60 kg. Pigs bred for bacon production are known as baconers and are sold at an age of around 24 weeks. They have a higher body fat ratio than regular pigs and can weigh up to a whopping 100 kg.
There are several different varieties of bacon. Middle bacon rashers possess the familiar bacon shape, that is a thin strip of belly pork with a lean round piece of loin at one end. Streaky bacon is the same cut minus the round loin end. Picnic or café bacon is various off cuts of pork that are pressed into a pseudo-bacon shape and should obviously be avoided. Gammon is a specialty of the United Kingdom that is a joint of pork - not the belly, that is cured and prepared in the same manner as regular bacon.
Just as there are a large variety of bacon styles, there is an equally large array of cooking methods, depending on the dishes country of origin.
In Britain and countries influenced by their cuisine, such as the United States, Australia and New Zealand, bacon is cut into thin rashers, then grilled or fried. It is generally considered a breakfast dish, witnessed most often in the famous dish of bacon and eggs. In Germanic countries bacon tends to be cut into thicker slabs, then poached or braised. The cooked bacon is often served up with an accompaniment of cabbage or potatoes. This is rich and robust fare perfect for colder climates. French influenced cuisine tends to use bacon as a flavouring agent, rather than a solo ingredient. This is typified by lardons, which are small dice or rectangular strips of bacon that are cooked at the beginning of a dish to enrich the final result with a nice smoky, salty pork flavour.
Cooking bacon rashers
Anthropod pointed out that I have neglected to provide a method for cooking bacon. Right she was, but I realise that there is more than one way to achieve this. At work, I throw super thin bacon rashers on a Zanussi hotplate, 80cm x 80cm, angled to let the fat drain away. At home, I - and you, are not so lucky.
There are a few schools of thought. One is the "no extra fat method". This involves placing the bacon rashers in a cold fry pan or skillet with no oil. The idea is to slowly bring the bacon up to heat and cook it at a very low temperature for 15 minutes or so, avoiding any spitting fat and gaining a nice crisp texture at the same time.
I personally tend to add oil to a hot pan before adding the bacon - I find it sticks less. And lets face it, adding a tablespoon of polyunsaturated oil is little to worry about in the face of the cholesterol hell that is bacon. Whatever method you choose, always use a good nonstick pan, never aluminium or stainless steel, otherwise more bacon will end up in the sink than on your plate. Roninspoon mentions that he likes to use a cast iron pan for cooking bacon, the thought being that the bacon sticks to the pan just enough to prevent curling and get it crisp, yet not enough that it permanently adheres to the base of the pan. Sounds like good advice to me - but remember as Roninspoon himself states, cast iron can be "…a pain to clean.."
If you really prefer to add no extra fat, a method I use at home a lot may be of interest. Simple place the rashers on a baking sheet and set under an overhead grill (broiler). This method gets your bacon really crispy, but not so greasy.