imc

Expanding the left side, we have $x^2+2xy+y^2=x^2+y^2⟹2xy=0⟹xy=0⟹x=0\text{ or }y=0$ Thus there are two lines described in this graph, the horizontal line $y=0$ and the vertical line $x=0$. Thus, our answer is $\boxed{\text{twolines}}$.