Fly fishing, simply put rather than concisely, is fishing with the use of artificial bait, or a lure if you will, that resembles one of many flying and non flying insects. Most artificial lures resemble aquatic life, such as small fish or frogs, but a "fly" resembles terrestial insects.
The hook is "decorated' with a variety of yarns, hackles and other feathers to distinctly imitate a certain specific insect. The varieties of "flies" available are by the thousands from ants to zoea larva.
The "fly" is usually presented with a special rod called a "fly rod". It has a large diameter floating line (usually) and a simple 1:1 ratio large diameter reel. The leader (tip) of the flyline is of 2-4 lb monofilament line, of which the fly is tied to.
The rod is usually 8 feet or more in length for better casting.
The idea is to entice the fish into striking the fly as the fly is repeatedly allowed to strike the water by using a slight whipping motion with the rod. This imitiates the action of a flying insect that is flying just above the water level. There are several methods to present the fly such as the roll cast, side cast, back and forth action and simple still fishing.
Fly fishing differs drastically from lure fishing by means of the tackle, the weights of the artificial lures and the action of the actual fishing process involved. Standard aritificial lures weigh anywhere from 1/8 of an ounce to 1 or 1 1/2 ounces, while "flies" are measured in grams and hook sizes. A fly will seldom weigh more than 1/8 of an ounce.