Derivative:The derivative of a function represents its rate of change at any given point. For a function to have a horizontal tangent line at a specific point, its derivative must be equal to zero at that point.
Slope:The slope of a curve represents how steep or shallow it is at any given point. To have a horizontal tangent line, the slope of the curve must be zero at that specific point.
Critical Point:A critical point occurs when either the derivative does not exist or when it equals zero. Having a critical point can indicate the presence of either vertical or horizontal tangent lines.