Difference: the business is different.
Bank: Mainly engaged in indirect financing services. Suppose a group of people or enterprises have extra money, let's call it A, but there are other people or enterprises in the economy who are in urgent need of money but have no money, let's call it B. The role of banks is to act as middlemen, absorb deposits from A, and then lend money to B to earn spreads. Both A and B are directly related to the bank, but A and B are not directly related. Even if B can't return the money to the bank, the bank must return the money to A. ..
Securities: mainly engaged in direct financing services, or the above assumption that A has spare money and B is short of money, A doesn't know that B is short of money and B doesn't know that A has spare money. The role of a securities company is equivalent to an introducer, bridging the gap between A and B, allowing A and B to have a direct relationship, and collecting commissions and handling fees from them. At that time, if B goes wrong, A will bear the consequences, and the securities company has no obligation to pay compensation.
Insurance: Why is insurance also a financial institution? Because insurance companies are similar to banks, they have the function of absorbing social idle funds and investing. Insurance companies collect premiums from the insured, and then use them to invest and earn profits, ensuring that there will be profits after paying the fees. In essence, it is also collecting money from A and then investing in B. It is just a form of expression with the bank. The bank will eventually return the money to the owner of A, and the insurance company will eventually return the money to some people of A, but the amount returned to everyone is higher, which is what we usually call claims settlement.