Whatever is not absorbed into the bloodstream moves into the large intestine and will become waste.
The watery waste moves through the large intestine by peristalsis.
The job of the large intestine is to solidify waste for excretion (aka make POOP).
If the large intestine absorbs TOO MUCH water, waste becomes super hard and constipation takes place.
If the large intestine does not absorb enough water, waste remains watery and diarrhea takes place.