The expression "-x^2" represents a quadratic function where the variable x is squared and then multiplied by -1. This means that the graph of the function opens downward, creating a "U" shape that is inverted. The highest point of this graph is called the vertex, which occurs at the origin (0,0) when there are no additional constants added. In this function, as the value of x increases or decreases from zero, the value of "-x^2" becomes more negative. This indicates that the function decreases without bound as x moves away from the vertex. The function is symmetric about the y-axis, meaning it looks the same on both sides of the vertical line at x = 0.