The document describes the passing of parameters in a stack during procedure calls. It shows a main program that defines two variables NUM1 and NUM2, pushes them onto the stack, and calls a subprogram SOMMA. The SOMMA subprogram saves the stack pointer, moves the base pointer, adds the values at specific offsets from the base pointer, restores the base pointer, and returns. This animation illustrates how the parameters are passed on the stack and accessed by the subprogram.