It is a pair of waterproof suspenders that are either paired with a pair of waterproof boots or with a pair of neoprene socks. With a pair of wading pants, you can wade in water without getting wet. The boots are almost always made of rubber, while the pants are often made of PVC coated textile (galloon), neoprene, or rubber.
There are two different common models, and these are bootfoot waders and stockingfoot waders.
Bootfoot. This model is more common on the cheaper variants. Typical for this model is that the wading pants are paired with a waterproof boot. The advantage is that you don't have to spend money on a pair of separate wading shoes. However, if you are going to walk longer distances, this can be a disadvantage, as the boots are not as comfortable as a pair of your choice.
Stockingfoot. This model has no boots, but at the end of the wader pants there are a pair of neoprene socks attached. The only drawback is that it is a more expensive option because you have to buy a pair of suitable wading shoes. The advantages are that you can choose which boots you want and find a pair that fits your feet perfectly.
It depends on the type of water you should use your pants in. If you are only going fishing in shallow water, a pair of waist waders is a smoother option, as these resemble a pair of regular pants more than a pair of chest waders. With a pair of waist waders, you can also move your upper body more freely. Chest waders are the most common model and make it possible to wade out at chest height, which allows you to use them in any type of water.
For most manufacturers, the size of the wading pants is associated with the size of the sock or boots. This makes it difficult to find a pair of perfect size. Since different manufacturers' sizes differ, it is best to start from each manufacturer's fit and then test your way through. However, be sure to choose a size where you can fit other clothes underneath.