I was wondering if anybody knew that is low lower than keep warm on a crockpot?
No, low and high are hotter settings intended to actually cook food.
Warm is a setting used to hold food that’s already been cooked (and is already hot)
Update: ‘warm’ may not keep the food above 140°F and out of the ‘food danger zone’. As some slow cookers just send a constant amount of energy, they do not correspond to specific temperatures (which is further dependent on what’s in the cooker, if it’s lidded, etc).