What happens to leftover restaurant food at the end of each day?

Before i entered my rookie classes at my police academy, i was a police dispatcher for a year. working the night shift, the manager of a local Kentucky Fried Chicken restaurant, would bring the daily leftover chicken to us. there was never a charge for the food. he stated, “i had rather give you guys the leftover chicken, than throw it away”. we really did like that man. Question: if this much food is left over each day at just one restaurant, then what happens to leftover food at all the other restaurants?