Light Boots (Class A and B)
Light boots are sometimes called hiking shoes or even "tennis boots." They are low-cut shoes with hiking boot-style treads, and are typically made from nylon, leather, suede or a combination. These boots are meant to provide a comfortable, flexible, light shoe that is rugged and offers more grip than the typical cross-trainer shoe. Light boots should be light and comfortable, and their stylish appearance makes them popular casual footwear. They may or may not be waterproof and they offer no ankle support. This combination of factors makes them ideal for day hikes on easy trails, especially for those not carrying loads over 25 pounds.
Mid-Cut Boots (Class B)
Mid-cut boots are what many people imagine when they think about hiking boots, and it is best to think of them as scaled-up light boots. They can be made from leather, suede, nylon and sometimes GORE-TEX, or a combination of material. But mid-cut boots are usually meant to be waterproof, so nylon is not as commonly used as with light boots. A boot made from nylon mesh and leather optimize ventilation for hot conditions and are not waterproof. The mid-cut design of these boots offers more ankle support, making them suitable for light off-trail, carrying middling loads (up to 50 pounds) and for multiday hiking. This type of boot is popular among outdoors enthusiasts, as it is suitable for tasks like hiking into a primitive campsite at a state park, hauling a kayak down a steep slope to a riverbank or carrying photographic equipment to a bird-watching perch.
Heavy Boots (Class C)
Heavy boots are meant for heavy off-trail use and carrying serious loads. Standard features include heavy-duty construction, waterproofing, high-cut design for extra ankle support and a protective toe cup. These boots are made to at least the three-season standard (spring, summer, fall), with the four-season standard being common. However, unlike light and mid-cut boots, these boots are not made with comfort in mind. Their rugged construction requires a substantial breaking-in period, and they are heavy enough that only a back-country hiker or mountaineer in training would consider wearing them on the street on a regular basis.
Mountaineering Boots (Class D)
As the name implies, these boots are for climbing mountains. They are built for use in cold weather and in the most rugged conditions, and are designed with crampon-use in mind. Mountaineering boots are so stiff that they are almost akin to ski boots. The lack of flexibility and their sheer weight means they are rarely worn away from their intended purpose.
Another kind of boot is the wet boot, which is entirely separate from its land-based cousins. A zip-up mid-cut boot made from neoprene with a thin, treaded sole, these boots are intended for water sports. They offer little support and are meant mostly to protect the feet from underwater rocks and to keep them warm during a prolonged submersion. A kayaker, for example, will probably switch to wet boots for getting in and out of the river after hauling his kayak down to the riverbank wearing mid-cut boots. These boots are also popular with snorkelers, scuba divers and surfers.