Whenever you create a customer (person or company) the new account bonded to the customer is created. We call it current account and it is the main account for all operations with the customer.
For example, a customer wants to deposit savings account. He should give the deposit amount to the teller, after that, teller transfers money to the customer's current account and, finally, deposits savings from the current account.
The same process in withdrawal case: money from savings transferred to the customer's current account, teller withdraws from it and issues asked amount to the customer.