The question is asking for the lowest $y$-value (or the minimum point) of the function depicted in the graph.

From the graph provided, we see a parabolic curve that opens upwards. The vertex of this parabola represents the minimum point since it is the lowest point on the graph.

• The vertex is at $(0, -1)$, which means the lowest $y$-value the function reaches is $-1$.

Thus, the lowest $y$-value of the function is $-1$.

Would you like further details, or do you have any questions? Here are five related questions:

1. How do you identify the vertex of a parabola from its graph?
2. What is the general form of a quadratic function, and how do you find its vertex?
3. How does the orientation of a parabola (opening upwards or downwards) affect its minimum or maximum values?
4. What is the axis of symmetry in a parabolic graph, and how can it be determined?
5. How can you calculate the vertex of a quadratic function algebraically?

Tip: For a quadratic function $y = ax^2 + bx + c$, the vertex can be found using the formula $x = -\frac{b}{2a}$.