Explain the difference of two sets.

The difference of two sets is found by comparing the elements of two distinct sets. To do this, you use one-to-one correspondence to create pairs of identical elements that exist in both sets.

The "difference" then refers to the elements that are left over in one set because they could not be paired with any element from the other set using this one-to-one correspondence. These are the elements unique to that specific set.

For example, if Set $A = \{a, b, c\}$ and Set $B = \{c, d\}$, you would pair the common element $c$.
The difference $A \setminus B$ (elements in $A$ but not in $B$) would be $\{a, b\}$.
The difference $B \setminus A$ (elements in $B$ but not in $A$) would be $\{d\}$.