Integration symbol help

Since doing some integration in calculus, I've encountered something that has made me somewhat confused.

Integration sign shall be written as S.

Take this question as an example:
1 dx
S -----------------
0 Sqrt(4-x^2)

Can someone please explain what the little one and zero at the top and bottom of integration sign mean? Does it change how to solve the question, or is it some sort of a limit to the question?

It is an indication of the two values that the integral should be integrated after you take the antiderivative. Say you have ∫[x=0 to x=1] xdx you take the antidervivative of whatever is in the integrand first. The anti derivative of x is x^2/2 so then you evaluate that from 0 to 1. So it look like [(1)^2/2]-[(0)^2/2].

they are called upper and lower limit, you can put these values after integration if for a question the solution after integration is 4x-2 so

{4(1)-2}-{4(0)-2}
2+2
4