Basel II is a set of rules that banks have to follow to make sure they are safe and don't take too much risk. Basically, it helps banks know how much money they need to keep on hand in case something bad happens. It also helps them make sure their investments are good for their customers and for the economy. Banks need to figure out how much money they should have to cover their investments and customers if something goes wrong. The Basel II rules help them do that, so customers can be sure their money is safe.