There is 3 relations between sets: superset, subset and equal.
Are there more relations between sets?
Are 3 relations include all the relations between sets that exist?
Assuming that you understand complement: Suppose that each of $A~\&~B$ is a set
1) The difference of $A~\&~B$ is $A\setminus B=A\cap B^c$ some authors use $A-B$
2) The symmetric difference is $A\Delta B=(A\cap B^{~c})\cup(B\cap A^c)=(A\setminus B)\cup(B\setminus A)$ some authors use $A\circleddash B$ or $A\oplus B$.