"Cash" is commonly used as a noun to refer to some element of physical currency.
The business is "cash-only." In other words, the business only accepts cash and does not accept other forms of payments such as checks or credit cards.
Do you have any cash on you? In other words, do you have dollar bills on you?
But cash can be used as verb as well, usually in specific situations, to mean change one form of non-cash currency into cash.
For instance: I went to the bank and cashed my check. In other words, I went to the bank and exchanged my check for cash.
