is the square root function. The graph of this function has been attached below. As you can see, this is in fact a function it passes the Vertical Line Test for Functions that establishes that if a vertical line intersects a graph at most one point, then this is a function. From the square root function we know:
The domain of the function is the set of all nonnegative real numbers.
The range of the function is the set of all nonnegative real numbers.