A look a the inner life of children when they are facing pain or trauma.
Because younger characters usually don't yet have a clear understanding of sorrowful emotions and their implications, they may deal with them in an indirect way.
Some films opt to represent these emotional explorations through filters, be them fantasy or pretend games, that can be deeply symbolic. Other films choose to show the children's turmoils through complete realism, avoiding the more comfortable and safe space of imagination.
They all hit me like a truck.