A bank lends only a small fraction of its deposits to its many borrowers. When banks accept deposits, it promises the depositor that it will repay the amount of the deposit if they want or need it. The bank owes for the deposits so they are a liability to the bank. When the bank loans money, the borrower promises to pay the bank. This is an asset to the bank.
Checkable deposits are deposits which checks can be written against.
Demand deposits are those held by banks that do not earn interest. There are different types of money or money aggregates. M1 currency coins, checkable deposits, and travelers checks M2 savings deposits, money market deposits, checkable deposits, currency and travelers checks. M3 time deposits, money market deposits, savings deposits, currency, traveler s checks and checkable deposits. M1 is the most narrowly defined category of money.