Double stepping is when a player moves one foot quickly to substitute for another foot.
Why[]
The reason commonly used for double stepping is a lack of knowledge, typically in the use of the Cross over when instead of moving there left foot to hit the right arrow, they will move there right foot from the down arrow to the right arrow.
The other reason is for Perfect Attack or Stamina, since it means you have moved less and also haven't got to twist to see the screen so your timing can be better determined during a cross over.
It's not just Cross overs of course that can be double stepped, Spins and streams can also be double stepped.