Are investment banks also called securities companies?

Not for a while, the main investment projects of investment banks are strategic investments, and there are two kinds of securities companies. One is called brokerage, which mainly serves stock investors. That is to say, we can't buy and sell stocks directly at the exchange, but we must open an account at the securities company. The other category is comprehensive, which includes not only brokerage business, but also its own investment, that is, the function of investment bank.