Difference of set A and B means

all elements of set A which are not in B

Let A = {1, 2,
**
3, 4
**
} , B = {
**
3, 4
**
, 5, 6}

A – B = {1, 2}

The blue region is A – B

##
**
For B – A
**

B – A = {
**
3, 4
**
, 5, 6} – {1, 2,
**
3, 4
**
}

B – A = {5, 6}

As B – A = All elements of B which are not in A