If it is', it means the derivative of the function.
Definition of derivative products:
If the function y=f(x) is differentiable at every point in the open interval, it is said that the function f(x) is differentiable in the interval. At this time, the function y=f(x) corresponds to a certain derivative of each certain value of x in the interval, and forms a new function, which is called the derivative function of the original function y=f(x), and is abbreviated as y', f'(x), dy/dx or df(x)/dx.
Geometric meaning:
The geometric meaning of the derivative f'(x0) of the function y=f(x) at x0: it represents the slope of the tangent of the function curve at P0(x0, f(x0)).