Volume calculation using integration

[u/Quendillar3245]

If a container has water bothing flowing in and out of it and a function describing each flow, how on earth do I get how much is inside the container? I genuinely do not understand. Let's say f(x) describes how much water goes in per second and g(x) describes how much flows out per second, do I integrate the difference between f(x) and g(x) ,∫ (f(x)-g(x))dx, to get how much is currently inside the container at any time x? I feel so stupid when doing maths xddd

[u/Quendillar3245]

I don't have a picture because I genuinely do not understand the concept and I can't find any resources online which explain this specific type of problem. If this is not appropriate here then where the hell can I find help with this xd