An alpine binding provides the connection between your boots and your skis. An alpine binding is the most common type of ski binding, and the sort that you’ll see most often at a resort. When shopping for a binding, you'll want to primarily consider the max DIN setting you need based on your weight and ability, and then the width of your skis relative to the width of the binding and its brakes. Other features that you'll want to consider include housing material (plastic or metal), toe height adjustability, and whether you want a strictly alpine or alpine/AT touring binding.
Ski width determines the width of the binding brake and mounting platform you need. A wide binding should be mounted to a wide ski, and a wide ski requires a wide brake. Most binding manufacturers offer a wide brake option, some of which go as wide as 130mm to accommodate mega-fat powder skis.
A binding’s DIN setting indicates how easily it allows your boot to release from your binding during a crash or otherwise. Your weight and ability level determine your DIN setting. DIN can be adjusted from as low as (.5) to as high as (20+), although the specific range depends on the binding.
Some alpine bindings can be switched between a free-heel ‘climb’ mode and locked heel ‘ski’ mode. This versatile type of binding is more mechanically involved than a dedicated alpine binding, but it can serve double-duty at the resort or in the backcountry.