Photo by Donna T. Ruhlman

Brine: A brine is salt in solution.  Brining is a powerful
technique for seasoning meat and fish and can also cure it and
introduce complementary flavors.  Fresh vegetables can be brined at
room temperature for a natural pickle, one in which the acid is
generated by bacteria.  Brine strength, the ratio of salt to water, can
vary but a good working ratio is a cup of kosher salt (between 6 and 8
ounces) per gallon which, depending on the type of salt you use will
result in a 5% to 6% brine.  For an exact brine, it’s easiest to use
metric measurements—50 grams of salt per liter of water results in a 5%
brine.  Always use kosher or sea salt, and it’s best to weigh the salt
rather than measure it by volume.  A 5% brine is also an excellent
liquid in which to cook green vegetables and
the ideal strength for natural pickles.  A small amount of sugar is
often added to a brine to counteract the harshness of salt.  Aromats
can be added to the brine to complement the flavor of the meat or
vegetables (tarragon and citrus for chicken for instance, garlic and
sage for pork chops, garlic and chillis for pickled vegetables).
Aromats should be simmered in the brine while the salt dissolves to
infuse the water.  Brines should be completely chilled before the meat
or vegetable is added and should be discarded after they’ve been used
(never reuse a brine).  The brined item should rest after being removed
from the brine to allow the salt concentration to equalize within the
meat.  A brined piece of meat, which has absorbed water, will result in
a ten to fifteen percent greater yield and often juicier finished meat.

–from The Elements of Cooking: Translating the Chef's Craft for Every Kitchen

The above image is from the corned beef soon to simmer in a spicy
liquid.  I used a five percent brine along with chilli flakes, mustard
seed, coriander, ginger, peppercorns, cinnamon, cloves, garlic and
importantly, pink salt
(which gives the meat its distinctive piquant flavor and rosy color).
Home-cured beef is fantastic, easy, and enormously satisfying (there’s
a complete recipe in Charcuterie).
I now find it difficult to enjoy a store-bought corned beef, not
because there’s anything wrong really with buying a brisket  that’s
been brined, only that having enjoyed so thoroughly curing my own I’m
acutely conscious of the pleasure I’ve deprived myself of by not doing
it myself.  And it doesn’t taste as good.
    One of the many
extraordinary uses we can put a brine to.  If all you have available is
crummy factory pork loin, second in it’s lack of taste only to the
factory chicken breast, brining it is a good way to make it more moist
and flavorful.  But again, I want to stress that a brine is a
multi-faceted tool: it’s a perfect medium for cooking green vegetables,
pickling vegetables (now, when it’s cool, is a good time to pickle
vegetables—keep cut root vegetables and aromatics submerged in a 5%
brine for a week and you’ll have a nice clean sour pickle), curing meat
such as beef or pork loin (for Canadian bacon) or shoulder or leg (for
ham), and enhancing the flavor and juiciness of meats we roast.