The dealer bears the maintenance expenses in a maintenance lease. The opposite is true in a non-maintenance lease. If the dealer provides repair and maintenance, you will need to bring the car to the dealership in line with the suggested schedule by the manufacturer to maintain the warranty coverage. (You will typically have to obey the manufacturer's scheduled maintenance in order to guarantee warranty coverage, even if you have to pay for the repairs.)
You pay the dealer a set amount for maintenance each month in what is called a budget maintenance provision. The dealer subtracts maintenance expenses that are incurred from your maintenance account. When the lease ends, you will make up the difference or receive a refund if more was deposited than used.