A browse through the egg section of any supermarket reveals an almost dizzying range of choice. You can have anything from small to extra large, brown or white, Omega-3 eggs, eggs from free-range or cage-free chickens (those two terms are not necessarily the same thing), vegetarian eggs (the chickens are given vegetar-ian feed, but this should also preclude them from being free range because when chickens forage, they eat insects), and eggs from birds that were fed kimchi, which is said to strengthen the immune system (not just of the chicken, but also of the person eating the egg).
First off, although many people think brown eggs are better for us than white eggs. They're not. The colour of the shell is determined by the breed of the chicken, and there are even some types that lay blue- or green-shelled eggs. The main factor that affects the nutritional content of the egg is what the chickens are fed. Most are given vitamins and nutrients, even if the labels don't boast about that. Also, the colour of the yolk doesn't always determine the egg's nutritional content: although deep yellow or orange yolks are usually associated with birds fed on corn, breeders can change the colour by putting additives in the chickens' diet.
Most commercially raised chickens - whether they're farmed for their meat or to lay eggs - lead a miserable life; they're kept in row after row of small cages. Cage-free birds are just that - but just because they're not in cages doesn't mean they're not raised in confined spaces. And neither does free range necessarily mean the birds can roam freely and happily in the great outdoors - regulations on precisely what free range means vary from country to country.
When it comes to cooking eggs, size matters - sometimes. It tends to be less of an issue with savoury dishes, but it can make a difference in dessert recipes. Most recipe writers specify the size (usually large) if using a different-sized egg would negatively affect the outcome of the dish.
Truc: (tryk): noun, masculine, trick, gimmick, device. A French word for a chef's secret.