Basically, sometimes, there will be a single page or a large portion of the page dedicated to a single scene or image, and this will be cut into panels. But if the gutters were removed, the image would be whole. So what purpose does cutting it do exactly?
The division in panels is used to signify the passing of time, occurring in the direction of reading. This is known as sequential narrative. Whether the panels consist of different images or divide what appears to be a single image, does not matter for this interpretation.
Often when it concerns a single image, this division is combined with text - be it dialogue, description, or thoughts of the person(s) depicted. It can symbolize a lack of physical or emotional change, a stability, solidification, or unyieldingness:
Adding to Joachim’s “passage of time” explanation and considering his example image specifically, composite images consuming multiple frames also consume more of the current page than conventional single frame images.
This greater scale may imply that the image contains greater drama, intensity or event some time-stopping significance to the depicted character.
It attempts to convey a horrible moment which stretches out towards eternity due to its mind-shattering emotional impact upon the subject of the image.