A manufacturing process is a function that turns inputs to outputs. We can think of it like a math function:
f(x) = y
In this simplified example x is all inputs, y is the manufactured good, and f is a transformation function that turns x into y. Of course we know that f is not necessarily one process, but multiple processes such that:
f(x) = g1(x) + g2(x) + ... gn(x)