Animism is a belief system (ontology) based on the completely outlandish notion that human animals and nonhuman animals have shared ancestry.
Outlandish huh. OK. In another way, animism is believing that your grandmother was a bear. Or that all bears are your grandparents.
Some people believe that all things, even rocks, rivers and clouds, have a spirit. They believe that humans are not the only people. Anything can be a person if it has a self or soul.
I have been trained as a scientist, and while I am not a great scientist, my training, and my postdomestic way of being means I am unable to fathom certain ways of thinking. Even as a child I would never have imagined that my gran could be a bear. I have also never had semiconscious conversations with animals. People in pre-domestic societies claim this happens all the time.