If $A = \{(x, y): x^2 + y^2 ≤1, x, y ∈ R\}$ and $B=\{(x, y): x^2 + y^2≤4; x, y ∈ R\}$, then

$A-B=\phi$

Region A (circle with radius 1 and center (0, 0))

Region B (circle with radius 2 and center (0, 0)) 

Clearly, A is the set of all points lying inside or on the circle with centre at the origin and radius 1 and B is the set of all points lying inside or on the circle with centre at the origin and radius 2 units. Clearly, $A⊂B$. Therefore, $A-B=\phi$ and $B-A≠\phi$.