If we suppose that this is formula for gradient descent method:
$$x_{n+1}=x_n-\lambda\cdot{{df(x)}\over{dx}},\ n=0,1,2,3,...$$
Since there is no exact value that we subtract instead of derivative, does it mean that we subtract value of derivative and use it only for controlling direction of next position of x? And why do we subtract derivative but not any other value that is depends on x?