Displacement is that in which less reactive metal is displaced by others and in double displacement reaction is in which two elements or a compound\’ions is displaced by other ions to form a other compound.

1 element of reactants reactions displays other reactants is known as displacement youTwo elements of reactions displace Each Other is known as double displacement
Displacement reaction is the reaction in which higher reactive element replaces the less reactive elementDouble displacement reaction is mutual exchangement of ions

Displacement means replacing one component of salt and double displacement is replacing both the parts of salts in reaction