Doubles refers to the 2 versus 2 part of a tournament, also referred to as "teams". Doubles requires a different strategy, namely teamwork, to defeat opponents. Although there are as many ways to play as there are players, several things remain constant: those who work together to attack and destroy their enemies stand a greater chance of winning, while those who separate to take on their opponents alone are easier to defeat as individuals by attacking them two-on-one. Strength in singles playing style does not necessarily translate into strength in doubles; the strongest team is the winner, not the pair of strongest individuals.
Doubles tournament rules
In general, rules for singles tournaments also apply to doubles except where otherwise noted. See tournament legal for all tournament rules.