The empty set contains no elements, hence what you are doing is removing no elements from some set, say $A$, which yields $A$, i.e. $A\backslash \emptyset = A$.
Now take $A$ to be the empty set.
The empty set contains no elements, hence what you are doing is removing no elements from some set, say $A$, which yields $A$, i.e. $A\backslash \emptyset = A$.
Now take $A$ to be the empty set.