Hi, im 15 years old and I became fasinated about these sumbjects of integral and differentiation. My question is, as far as I know integral is used to calculate area under a curve but I dont know why in many physics equasions its been used where there is not even a graph and a curve to find the area!! The question doesn't even ask to find any area but still I can see Einstein used lots of integrals in general relativity. I mean where would you use integral or differentiation even though no graph and no curve is given and no area is needed to be found. Note: I might not be even right in my question, if so please point it out. Thanks.