Understanding the Fundamental theorem of Calculus in plain english I am learning Calculus. I am trying to understand the fundamental theorem of calculus. I am following this wikipedia article: https://en.wikipedia.org/wiki/Integral.
I am having a hard time understanding what they refer to as the the Fundamental theorem of Calculus. Could someone kindly explain to me what it is in plain english. The wikipedia article is quite gibberish.

The FTC says that integration and differentiation are inverse operations.  If you differentiate the right kind of integral, then you get the integrand back.  If you integrate a derivative, you get the original function back.  
D(I(f))  = f
I(D(f))  = f.
