Exponential growth function has a form
where A is the initial value and r is the growth rate.
If we substitute x=0 we obtain `y(0)=A*(1+r)^0=A.` Recall that y-intercept is the point on a graph where x=0. So A and the y-intercept are the same.
So the answer is: the y-intercept is the factor of the function and the growth rate plus one is the base of the exponential function..