With this technique, users replace their own body with some other object, generally with a block of wood, the moment an attack lands. This creates an optical illusion, making the enemy think the attack was successful. From this, the user can use the lapse in the enemy's attention to attack or flee from the battlefield. Explosive tags can be attached to the replacement for an added surprise. It's a basic ninjutsu even taught at the Academy, but it's a useful art that can be applied in variety of situations.
This technique is based on a real-life ninja art, kawarimi. It was an ancient ninja art revolving around misdirection and the split-second timing of a switch between a 'body' and a location, or between two or more bodies: A technique utilised by ninja in ancient Japan, involving the ninja and anything that can be mistaken for them, (such as a dummy or a mannequin). As it means "a quick shift in position, or adaptability to changing circumstances", it is also utilised in Sumo.
This technique is sometimes referred to as the Empty Cicada Technique (空蝉の術, Utsusemi no Jutsu) in other stories (not to be confused with the Empty Cicada Shell Technique, which bears the exact same kanji). This name refers to the empty shell a cicada leaves after moulting.