Provisions are food supplies gathered by your troops whenever they are in a region with a surplus production of food(the region produces more then it consumes). Then, when they enter a starving region, they can eat the provisions instead of immediately starving. Provisions are gathered or eaten at the dawn turn change. Provisions are gathered at a rate of 10% per day and eaten at the rate of 20% per day, meaning that a unit can stay in a region producing a surplus of food for 10 days in order to stay in a starving region for 5 days. Provisions can also be bought in friendly regions with an open granary.