A check is a document that is written, dated and signed that instructs a bank to give a specific sum of money to the person or entity noted on the check. The check has your account number written on it so the bank knows where to find the money and can make sure you have enough money in our account to send.
When you write a check for an amount in excess of the sum of money available in your account, your check can be rejected for insufficient funds and in the event, the bank chooses to honor your check, you could be charged what’s called an overdraft fee and the balance on your account will go negative until you deposit enough money to cover the overage the bank covered to honor your check and the fee they charged for doing so.