Can someone explain what this question is asking me? (Calculus II) How to define the area of the region bounded by $y = \sqrt{1-x^2}$ and $y = 0$?

I am assuming we will be using Riemann's sum however I am not sure if we are given $[a,b]$ or is that what we are given?
Hint:

The graph of $y=\sqrt{1-x^2}$ is the unit circle $x^2+y^2=1$ with range $0\leq y\leq 1$.

The region is exactly $\frac12$ of the total area of the unit circle.
the resultant area is the area inside the circle and above x-axis

so area is equal to $\pi r^2$/2 where r=1

and hence the area is $\pi$/2