Mathematics
Partial Derivatives and the Gradient Vector in Multivariable Calculus
Quick fact
The gradient vector always points in the direction of steepest ascent of a multivariable function, and its magnitude equals the slope in that direction. This single vector encodes all the partial derivatives of the function at a point.
Why this is interesting
Imagine you're standing on a hillside in a thick fog. How can you know which way is the steepest climb without seeing the whole mountain? The answer lies hidden in a vector that calculus can compute.