Ski bindings are both a performance and safety item for your skiing. They help you ski better and their release settings should protect you from a broken leg by letting you get out of your ski when you take a bad fall.
There are different types of ski bindings for the type of skiing you are doing whether it is alpine, cross country, telemarking or even jumping. The ski binding is what keeps you grounded. ski bindings transfer your energy to your ski.
Alpine Ski bindings attach your toe and heel to the Ski. Cross country bindings allow the heel to be free for better gliding. The telemark binding combines both. The heel is allowed to go free when hiking, climbing or walking, then clamped down for the descent.
The most common type of alpine binding is the step-in binding. The toe and heel pieces of a binding come in all shapes, sizes and technology. The tow piece normally has a sideway release. The heel piece usually allows your Ski boot to detach upwards and forward. There are brands that do it the other way around - so you have to educate yourself as to what fits your level of Skiing Skill and type of Skiing you will be doing.
Ski bindings should have a release adjustment. Your Skill level, Ski boots, height and weight are determining factors of where to set the release function on your bindings. There is something called a DIN scale that is an international standard for how bindings release. You don't want the release setting too loose or too firm. Either way spells disaster for your Skiing enjoyment. This is an area for an experienced professional. Make sure you talk to them at the Ski shop or sports store about your level of Skiing experience and Ski boots if you have purchased them elsewhere. It's always best to get a system of Ski, boots and bindings at one place from a reputable distributor or seller. Once you get a better on-slope feel for the bindings, you can do a little tweaking of your own. But when you start out with a new set of bindings, let the pros do the initial setting.
When a Ski bends in a length-wise direction it puts negative energy on the binding. Look for equipment that has an adjustable forward mechanism to be sure the binding's heel piece is putting forward pressure on the Ski boot.
The bindings should have an anti-friction device which helps with the sideway release of the toe. Many of these devices just have smooth surfaces to help the toe release. Some manufacturers, however, have developed technology to more aggressively assist in the release.
Some bindings allow you to move the bindings forward or back on the Ski. This allows for an adjustment to different Ski conditions like deep powder where you want your weight back and Ski tips up to navigate the terrain.
If you are an advanced, aggressive Skier, you may want to look at a binding that helps in vibration dampening for high speed, moguls or carving on ice.