to secure money placed in banks: The FDIC insures deposits in case of bank loss.
Bank failure in the Depression was the result of bad investments and then loss of individuals money. When people asked for their money back, they were unable to because they had lost the money in their bad investments. The FDIC is a federal insurance program so a person's money would not be lost if the bank invested poorly.
FDIC was created to secure money placed in banks. This was primarily due to the bank failures that arose with the Great Depression. People lost so much money due to the banks giving out bad loans. FDIC now ensures that should something happen, banks are required to have money on hand so that they can give you the money that you had with them.