It's nothing - not even a thing. An abstract ambiguous concept. A symbol of something undefined - of an idea
Previously they had one ship, one cow, one cat or small pebbles - each signifying a concrete individual aforementioned non-human person. Then the Sumerians got so affluent and lazy that they gave up on calculus, and after that the human civilisation crumbled like clay tablets on which they drew their disembodied signs.
There's still hope, though: Californian schools plan to reintroduce the old system https://www.wsj.com/articles/california ... 1621355858