Skiing and boarding take place on a surprising variety of mountainsides. Depending on where you go, you may find yourself on defined trails specially cut through dense forest, alpine pastures with forests around and rocky peaks soaring above, high and exposed (treeless) terrain that underneath the snow is essentially rocky or super-high and very exposed glaciers.
Trees are a key part of the character of some resorts, entirely absent in others. The tree-line (the upper limit of altitude at which trees thrive) is much higher - as much as 1000m higher - in North America than in Europe, with the result that the great majority of American resorts offer mainly forest runs.
Obviously, the steepness of the slopes varies widely too. In some resorts, practically all the slopes are so gentle that they can be tackled by someone only just off the nursery slopes. In others, most of the terrain appeals only to near-experts. But of course most resorts you can chose for your ski holidays manage to offer a wide range of difficulty so as to attract a wide range of visitors.
The steepness of the runs themselves is of course independent of the basic steepness of the mountainsides, because the trails can zig-zag gradually down the mountain. American resorts are particularly good at creating (and signing) an easy way down their mountains, so that near-beginners can taste the excitement of long runs from the top. In the Alps, these things more often come about by accident. In some resorts, snow-cover means that Alpine roads are converted into gentle winding runs in winter.
Pistes and trails
Most people spend most of their time skiing on defined runs known as pistes (the French term) or trails (the American term). Going outside these runs - going off-piste - requires equipment, skills, preparation and information that are not normally needed, and introduces extra risks. Boarders are much more inclined to venture off-piste than skiers, for the simple reason that deep snow is much less problematic for them than for skiers.
Pistes are defined usually by name or number and unless they cut through forest they are marked on the ground with poles (usually at both edges but sometimes one edge or the middle). They are plotted on a map that is given away in the resort. Pistes are opened only when safe (when there is no appreciable risk of avalanche, and when snowcover is adequate). They are checked out at intervals (and particularly at the end of the day) by patrollers, so that people immobilised by injury are unlikely to be left to freeze to death. Most pistes are "groomed" (an American term, originally) by tracked bulldozers to pack down fresh snow into a dense surface and to smooth out the bumps that skiers make in old snow.
Pistes are also graded for difficulty. Sadly, this doesn't work as well for the visitor or potential visitor as you might expect. For a start, there are different grading systems.
In Europe, the basic grading goes from blue (easy) through red to black (difficult). France adds green, effectively splitting the blue category into green (really easy, in theory) and blue (not quite so easy). In North America, the grading goes from green through blue to black, with no red. America uses shaped symbols, too (circles, squares and diamonds). At the top of the scale are double black diamonds, or even occasionally triple black diamonds.
These two scales are difficult to relate, even in theory. American single black diamond runs, in particular, tend to embrace runs that might be graded red or black in Europe. American double diamonds start with runs that would be genuine blacks in Europe, but go on to include much steeper runs than you will find in any European piste network.
When considering a visit to a particular resort you need to treat piste gradings with some scepticism. The most you can expect is that the gradings will accurately reflect the relative steepness of the slopes within that resort.
Pistes are reached by lifts. So are many off-piste runs. But keen off-piste skiers and boarders are increasingly prepared to hike up beyond the top of the lift systems to get to runs that offer special thrills (or simply to get to fresh snow).