Intussusception is a condition where one part of the gut (small intestine/bowel) becomes sucked into the next part of the gut. It is sometimes described as the intestine being 'telescoped' - imagine a telescope, where one part slides into the part next to it.
This is a companion discussion topic for the original article at https://patient.info/digestive-health/rectal-bleeding-blood-in-faeces/volvulus-intususception