Length, waist, and radius classification:
Race Stock Skis:
Down Hill: 210cm - 215cm; 45m radius; DH racing
Super G: 205cm - 210cm; 33m radius; SG racing
Giant Slalom: 180cm - 190cm; 21m radius; GS racing and highest level hard snow carving
Slalom: 155cm - 165cm; 10m - 14m radius; SL racing and highest level hard snow carving
Giant Slalom: 170cm - 185cm; 16m - 21m radius; A notch below full on race stock skis that allows the pilot to ski on snow other than hard pack and ice. Newer retail GS skis tend to have a similar construction to their stock counterparts with slightly smaller, more user friendly and crowd friendly turn radii. Still at home in a race course.
Slalom: 150cm - 170cm; 10m - 14m radius; Same caliber ski as a retail GS ski. Often are softer torsionally and stiffer longitudinally to allow for mistakes that the user may make. Overall, will ski better all over the mountain and last much longer than a race stock ski. Due to the short length and terrain that they prefer (ice), slalom skis tend to require tuning more frequently than normal skis.
Race Carvers: 150cm - 185cm; 11m - 21m radius; These skis can come in either a slalom or giant slalom variant - often depending on what length is preferred by the rider. These skis will fall in the company's race ski section just below their retail race skis. They usually share similar construction with the race skis, but offer softer flex and smaller radii. They will often have narrow waists and are built to excel on groomed snow, with the ability to be run in a race course and a bump run back to back.
Ski Cross: 160cm - 190cm; 16m - 21m radius; 65mm - 70mm wasit; Like the name says, the purpose of these skis is derived from professional SkierX competition. Although professional competition ski cross skis are actually remasked race stock GS skis, these skis serve the purpose to provide a wider platform race ski for the public to enjoy. Most skis in this category share a similar sidecut to a GS race ski, the only difference being that the ski cross ski is about 3mm to 5mm wider throughout the entire ski. The extra width allows the ski to be more predictable and handle varied terrain much better than a GS ski would - allowing the user to carve race type turns, hit jumps, and ski rough snow - just as they would in ski cross competition.
***Note: each category will contain skis that range from beginner to expert level skis***
Carving: 160cm - 190cm; 14m - 23m radius; 62mm - 66mm waist; A category that each season becomes more and more obsolete, the carving ski category provides skis that are mostly at home on groomed snow. They originated as a category that shared sidecuts with race skis, but as wider skis get closer to the performance of race skis, the category is evolving into wider skis with more sidecut. Despite the trend companies like Dynastar, and Volkl still produce a line of carving skis and the are still among the best performing skis on the mountain despite being over shadowed in the marketing media by their wider, shorter counterparts.
All-Mountain Short Turners: 150cm - 175cm; 10m - 17m radius; 66mm - 78mm waist; This is a new category that was started by the introduction of the Volkl 5-Star a few seasons ago. They usually have wide waists and deep sidecuts. The skis will ski like a slalom ski, but are usually much softer to allow to be skied all over the mountain. These skis are quickly becoming the rule for groomed trail skiing - especially in the east. Skis like the Atomic Metron series and Nordica Hot Rod series are bridging the gap between free ride skis and a typical slalom carver ski, as they fall into both categories. Other skis in this category are the Elan S12, Volkl Six Star, and Fischer RX8.
Freeride: 160cm - 200cm; 10m - 25m radius; 70mm - 85mm waist; A few seasons ago this category would have included skis 170cm - 180cm with a waist no wider than 75mm. Of course that was a few seasons ago, and now the trend is to go as wide as possible - especially if your ski area is prone to daily dumps, and your preferred terrain does not know what a snow cat looks like. Some of the skis in this category the rider will ski at a more traditional length (traditional as in 2000 - 2001 tradition, not 1980's traditional where a 140lb male was on 210's). These skis will ski anywhere. They will ski off piste, groomed, and bumps (think M1 tank). They do not however, excel on ice, due to their width, but if the rider does not mind sacraficing some groomed performance in return for a lot of ungroomed snow performance, this is your category. Western US skiers should shop here.
Powder: 160cm - 210cm; 12m - 30m radius; 85mm - 120mm+ waist; Two categories exist in the powder ski section. One category is the traditional powder ski - stiff flex, minimal sidecut, ultimately bomb proof. The other category, which recently has received more attention is the twin tipped powder ski category. These skis are becoming the new rule to powder skiing. They are typically slightly softer than traditional powder skis (some being noodles), and offer a deeper sidecut. "Carving" in powder can now be realized with these newer fat boards, and they are rapidly opening up powder skiing to skiers who never would have been able or willing to ski on a pair of fat boards. The downside is that while these skis excel in cut up snow and fresh powder, they are a handful on groomed snow, and require a seasoned pilot to get them to carve. Hardpack is out of the question.
Women's: 140cm - 180cm; 10m - 20m radius; 65mm - 100mm waist; Women's skis could actually be broken down into all of the above categories, but one explanation is enough. These skis span the performance and purpose spectrum, just like any other line of skis. Usually they are characterized by softer flex, mounting position farther foreward, and lighter weight. They will range from all-mountain short turners to powder skis, covering every range in between in order to offer beginner to expert female skiers skis that were built for their body types. Recently female skis are being built seperately from men's/unisex skis, and offfer the same performance levels as their mainstream counterparts.
Twin Tip: 140cm - 190cm; 12m - 20m radius; 70mm - 85mm waist; Also, a newer category (started by the Salomon 1080) these skis are designed with a twin tip, softer flex, mid-mounting point, and jumps and spinning in mind. Due to their soft flex, light weight, wide profile, and deep sidecut, they often can double as very good freeride skis. Skiers who are less interested in halfpipe and terrain park skiing will often mount these skis 2cm - 4cm behind their recommended mounting point and use them all over the mountain. They are truly at home in the terrain park and halfpipe but are fully capcable of venturing out of both.
Junior: 90cm - 170cm; <9m - 21m radius; 60mm - 75mm waist; Junior skis cover a huge range of skiers; from young kids to early teenage racers. Often these skis will have a weight limit, as they are designed for lighter riders, who are not as strong as an adult skier. They do not however, lack in ability on the snow. There is usually a line of race skis that is tailored to a few age groups, and a line of freeride skis tailored to the same groups. The end of the spectrum dedicated to older children offers very high performance equipement. The race skis are often built along-side their race stock adult counterparts in the race room, and offer pure performance tools with softer flex (less metal, foam core, etc.) for younger skiers. By the time a skier is 14 they are ready to branch into adult skis, or at least be skiing on the top end of the junior spectrum.
I think that covers most categories. Please let me know if I left anything out, and I will edit the descriptions or add a category.