Answer
See the image below.
Work Step by Step
$x^2+y^2\leq1$
Looks a lot like a general equation of a circle, with origin $O(0,0)$ that is: $x^2+y^2=r^2$
Where $r$ stands for radius of the circle.
The equation above, is a region of the circle with radius $1$. Less than or equal to sign means that the region given by the set is inside the circle, including the circumference.