The first step is to educate yourself - what exactly are we talking about when we hear "backcountry" or "sidecountry," and most importantly, what are the dangers associated with the terrain these terms refer to?
Knowing what these terms refer to is just as important as knowing where you're going, and what you're getting yourself into. Before you head out, it's important to be familiar with what risks you are willing to assume when you head out skiing in unpatrolled, and uncontrolled, avalanche prone territory. An excellent introduction to what it's all about just outside the resort boundaries or deep in the backcountry is the Utah Avalanche Center's basic "Know Before You Go" avalanche awareness video.
Resort Responsibilities and Your Lift Ticket/Pass
Resorts take responsibility for avalanche control, for providing a trained ski patrol to respond to injured skiers, keeping unruly skiers in line and assisting skiers in distress, but that responsibility begins and ends within the resort boundaries.
Some skiers and riders, more younger ones than older, are under the assumption that because they have bought a ticket or have a season pass, if they exit the resort through a legal gate, or even duck under the resort boundary rope, they can expect resort ski patrol attention to attend to them in an emergency - but this is not the case. It's imperative to keep in mind that you bought the ticket or the pass to ski under the auspices of ski patrol protection within the boundaries of the particular resort.
For many years ski resorts fought diligently to enforce legal penalties for exiting the resort boundaries, even if the skiers and riders openly denied any reliance on the resort's ski patrol. In fact, it was the resort's ski patrol responsibilities to chase and hold out-of-bounds skiers until local law enforcement could press charges.
However, after several threatened lawsuits against resorts for denying citizens access to federal land surrounding the resort boundaries, many ski resorts acquiesced and installed marked "access gates" mainly to keep a handle on the point of egress should emergency personal need to search for missing skiers or riders.
Jackson Hole Mountain Resort in Wyoming and the boundary battles that developed there is the most famous case of this, and their capitulation to out-of-bounds access was basically the first domino to fall and set the standard for other resorts that followed.
When the control gates were set and ticket and pass holders allowed to head off the resort-owned or leased land, they were heading really into what became to be known as the "sidecountry," and that definition is true to this day. So, if you use a resort lift to reach a gate leading to skiing and riding outside the resort boundary you are entering the sidecountry. Technically, even if you skin up and out a resort gate, you are still entering the sidecountry - think sidecountry to the resort property.
So considering that the term "sidecountry" refers to all the land immediately outside the resort, and as far outside as you care to travel either bootpacking or skinning, the fact remains that the resorts have no legal responsibility to have their ski patrol respond to any certain or perceived emergency, nor do the resorts have an obligation to do avalanche control work outside their boundaries. The 2012 avalanche at Stevens Pass that resulted in the deaths of three experienced and avalanche savvy skiers happened in the area known as Tunnel Creek - in the Stevens Pass sidecountry.
That is not to say that ski patrol, when called upon, won't go outside the resort boundaries to help in a dire emergency. But, it is usually after the incident has occurred, and usually is in response to a 911 call for help relayed by civilian protection services, such as the state or local police.
In short, if you ski the sidecountry through a resort access gate you are your own emergency first responder - know that you and your friends, while close to the resort land, can't rely on the terrain being avalanche-controlled or routinely skied for dangerous situations by ski patrol. You and your friends should be fully versed in the use of avalanche beacons, probes and shovels.
Important Sidecountry Information For Parents
It is especially important that parents and guardians who don't ski know what the sidecountry is, and that there is a lack of professional avalanche control and ski patrol protection associated with skiing or riding outside resort boundaries. When kids say "It's just outside the area, and I can see the lifts" that does not relieve them from any present dangerous situations or incidents. Once parents and guardians know this, they should insist that kids have the three tools necessary for avalanche rescue and know how to use them.
The most important difference between skiing sidecountry and backcountry is that the real backcountry is further away from any ski patrol supervision or resort-provided avalanche control. That's not to say that civilian avalanche control is never done in the backcountry, but that is usually limited to areas in which public roadways are near or under the path of known avalanche terrain.
Skiing real backcountry in the purist understanding of the term means that you access the terrain totally on your own power, usually from a recognized trailhead, but it can be from any point not in, or through, a resort.
While the basic tools - beacon, probe and shovel - and how to use them are understood as essential, travel in the backcountry carries with it the added personal responsibility of preparedness for a much wider range of dangerous situations which can arise from the remoteness of the terrain.
If you head out to ski the backcountry, familiarity with the area is obviously very important since getting to 'the goods' implies you have to get back. If you don't personally know the area, then you need to go with a qualified person who does. Qualified means someone who you trust to have the knowledge of avalanche tools and their use - remember, this person or persons are your first responders in an avalanche situation or other emergency.
The remoteness of backcountry is a big draw for powderhounds and for skiers who just like to get out in the midst of uncrowded nature. That remoteness also means you are farther from help in situations that might not seem catastrophic at first, but can quickly become very alarming. Think for a minute about what happens if someone falls, is hurt and unable to ski, if a binding breaks and is unusable, or someone suddenly gets very sick.
Of course, the first thought is to grab the cell phone or flag the ski patrol - but in the backcountry, cell service is a guess, and the ski patrol aren't there to help out, so you need to be able to respond to these variables on your own, or be with someone who can.
An excellent introduction to what it's all about just outside the resort boundaries or deep in the backcountry is the Utah Avalanche Center's basic "Know Before You Go" avalanche awareness video.
There are many ways to have fun in the backcountry but there are many ways a beautiful bluebird day of skiing can turn into an emergency situation that needs a trained responder. Ask yourself if you are prepared to be that person before you head into the backcountry.
There are other terms you may hear such as slackcountry and frontcountry and others that refers to skiable terrain outside resort boundaries but most all can be seen as sub-categories and/or closely related to the two umbrella terms - Sidecountry and Backcountry.