The range of flies is bewildering. It is possible however, to classify them into groups, but with some difficulty. Imitative flies copy some item of food. Suggestive patterns look like some item of food, but we are not sure really which one. Joke-flies (also called lures, hoodwinkers and super-killer-demon-bill's-orange-and-purple-thing) attempt to catch fish by an induced response. The unfortunate thing about these joke-flies is that nobody is entirely sure why they work, arguments have been raging for years. All I can say is that there are times when in order to catch fish you need to induce the take. To make things more accurate and yet more confusing, let me add that not all lures are joke-flies and that you can induce the take with all flies, even the dry fly. What follows is the list of different types of fly groups and their make-up. If anything is learned from the following I hope it is the difficulty encountered in a rranging flyboxes.

DRY FLIES sit on the surface and imitate adult aquatic and terrestrial insects. Some are tied with wings, which apart from in the imitations of sedge flies, have no apparent use whatsoever.
EMERGERS and semi-drowned insects sit in the surface, could also be classified as dry flies (sorry), also as damp flies and imitate the same stuff as before, but a little earlier in the aquatic life cycle and a little later with the terrestrial stage of submersion.
SUSPENDERS hang from the surface due to some buoyant part of the fly and imitate nymphs before hatching (and can also be called emergers, dry flies and a little later on, boobies).
NYMPHS are imitations of the aquatic stage of an insect, are fished (usually - but not always) sub-surface, somewhere between just under the surface to lying on the lake bottom.
WET FLIES can also imitate nymphs, sometimes they imitate drowned adult flies, more often they are food suggestive, occasionally they appeal more to the trout's instinctive reactions when they are used to induce the response.
There are three styles of wet fly designs;
Winged - which offers a colour contrast and little else.
Palmered - a bushy fly which can be dibbled (tripping the wave surface)
Spider - a sparse fly which is fished just below the surface and is quite nymphy.
LURES can either be fish imitations or take-inducers, are fished subsurface (with the exception of the muddler and the floating fry - which are fished in or on the surface) They are generally bigger than wet flies, however there exist patterns which are called mini-lures which are the same size as some wet flies.
MUDDLERS are buoyant lures in the large sizes and large dries in smaller ones which are pulled across the water surface, leaving a wake in the process. (They can also be used on sinking lines, where their success, is thought to be due to the underwater vibrations made)
BOOBIES are buoyant flies cast on sinking lines and allowed to float somewhere above the lake bottom.