The event begins with a qualification stage, when riders race on their own against the clock and the top 16 go through to the knockout stage.
Head-to-head rounds involve two races, with the rivals swapping sides after the first race to make sure neither receives an unfair advantage.
The rider who wins both races makes it through to the next round, and the combined times are used to decide the winner if each rider wins one race.
The final two riders in the competition compete for gold and silver, and the beaten semi-finalists face off for bronze.
Like the giant slalom in skiing, competitors must zig-zag between red and blue gates.
These are shaped on an angle so competitors can lean into the turns.
Flags are placed 20-25m apart and the vertical drop of the course is between 120m and 200m.
Riders who crash, miss a gate or fail to finish the first heat are given their opponent's time plus 4% of the top qualifying time. If it happens in the second run, their opponent wins, regardless of the result of the first race.
If both riders crash in the second heat, the one who passes through the most gates is declared the winner.
Parallel giant slalom is all about carving, so hard boots and plate bindings are used with a rigid board which can cut through the snow and give a stable and faster ride.
To cut down on air resistance, riders lean into the turns and wear skin-tight suits.
Most wear knee-height shin guards as they often hit the gates as they pass them, and helmets protect the head.
HOW TO GET INVOLVED
Snowboarding in the UK is possible at a number of venues indoors and out.
It might not be quite the same thing as riding on a mountain but you can snowboard at indoor slopes in England and at loads of dry ski slopes.
When it comes to the real thing there are loads of resorts to choose from in Europe which are no more than a short flight away.
For more information about snowboarding in the UK, check out the Snowsport GB website.
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