This section can be read in conjunction with section 1.05 which covers the different types of equipment that is used for each category.
Freeride
Freeriding covers it all. It is riding the whole mountain, taking in the conditions that are on offer as you meet them. Most people will fall into this category as they start out. Good freeriders will also encompass jumps and spins off natural kickers and cliffs.
Freeriders generally use directional boards and low/medium angles.
Freestyle
Freestyle essentially comes down to tricks. Tricks in the park or tricks in the pipe (or both). This is popular on glaciers in the summer as well as mountains that don't have a wide variety of terrain, as the rider aims to maximise the fun with the snow available. That said, even at moutains with masses of terrain, freestylers will be in the park and pipe in nearly all conditions.
Park and pipe preparation has become a big marketing point for the mountain resorts all looking for your custom. Big jumps are built by piling up the snow, but also by covering natural or even man made objects. Pipes used to be built as and when there was enough snow to cut one, but these days, concrete pipes may be built over the summer so when the snow falls, a minimal amount is required to get going.
No park these days is complete without a set of rails to slide on, jump onto, or off of. Rails are probably the fastest growing sector of the sport today.
Freestyles generally use twin tip boards that work the same no matter which direction the board is going. They will also run with low angles (or duck stance) to enable riding switch.
Alpine
This is the carving category, where the riders are aiming for fast clean carves whilst being lent over as much as they can... you could liken it to a sports motorbike cornering at high speed where the rider has his knee on the floor and the bike cranked over. Carvers will aim for the freshly groomed runs before everyone cuts up the snow.
Carvers generally use very directional boards (sometimes with a square tail) and hard boots with high angles.
Backcountry
Backcountry is basically freeriding, but outside the confines of a resort, ski area, marked terrain etc. It sort of falls into the freeride category - but I feel it warrants its own mention because it takes freeriding to another level. Whilst the goal is to ride all the mountain, it's generally aimed to be done in powder. Anyone that goes to the backcountry enough will tell you that it's not always powder that they find out there.
There is also the avalanche risk that you don't ordinarily need to consider within the bounds of a resort. If you don't know how to look for avalanche danger - don't go to the backcountry, not even to follow someone else... they may not know what they're doing - even if they have "all the gear". You could trigger an avalanche and wipe out a whole village. Seriously.
Serious backcountry riders will have "big guns", very long directional boards to give them the stability required at the speeds necessary to float over 6ft of powder. Of course, not everyone can get this kind of snow, and most of us will be happy with a normal (but longer) directional freeride board.