All right, so whatever isn't absorbed, like fiber, continues its journey onward through the ileocecal sphincter and into the very last part of the gastrointestinal tract: the large intestine, also known as colon.
The main job of the gastrointestinal system is ingestion - taking in food, digestion - breaking it down into nutrients, absorption - pulling these nutrients into the bloodstream, and finally, excretion - getting rid of waste.