Bol is obtained when items are picked up from UMAs,digging holes, kicking pots/grass, and defeating bosses. When Corobo sits on his throne with items in his inventory, these items are tallied in a list of what the item is, and what the item is worth.
In the beginning when a member of the Royal Guard dies, it does not cost anything. However, later on in the game there will be a "Death Benefit", which will take away from the total Bol that is accounted.
Bol is used when Corobo purchases items and upgrades in the Kingdom Plan and changing jobs of the citizens. There is a string of quests where Liam and Verde will ask about pay. Liam's pay starts at 100,000 Bol and increases by one thousand, while Verde's pay starts at 200,000 and increases by three hundred.