Bank deposit simply means that you or your company place money in the bank.
This is considered a very secure way of storing money, with a government guarantee at the bottom: In Australia, The Financial Claims Scheme (FCS) guarantees AUD 250,000 in deposits per legal entity (either a company or an individual), if something were to happen to the bank.
When individuals and companies deposit money in banks as bank deposits, this ensures that banks can lend money to their customers again.
Bank deposit = liquid assets
Cash in the form of bank deposits is just one of several ways to store value. Other forms can be stock savings, stock portfolios, investments in real estate, equipment, etc.
Bank deposits are one of the most liquid ways to store value because they consist of available cash. There’s no need to convert them into marketable assets through for example selling real estate, making them a good option for immediate financial needs.