A Girokonto is a "checking account". Stockbrokers/dealers allow you to write checks against the free cash portion (i.e. brokerage checking account) of your stock portfolio. The collective cash balances of brokerages are called the "money market". E.g., when I move money from my bank account by check to my brokerage account, I always write "Money market" in a reserved box so they know it is not to pay for a specific stock purchase but to be assigned to the "money market", i.e. the idle cash sitting in my brokerage account, to be redeployed at a later time (or not deployed at all). In the vernacular is is also called "to be parking cash".