We assume that the triple integral I= ∫∫∫ f(x,y,z) dx dy dz can be very useful in many situations, the simplest of which is mass calculation with non-uniform density.
If the total mass M is distributed over a volume, we can represent how this mass is distributed with a function f(x,y,z) which gives the density at the point (x,y,z).
If you integrate over volume, you can calculate the total mass.