I suppose the answer to that question these days is “all sorts of things,” but it wasn’t always so. After the 1929 stock market crash, the US enacted laws that put limits on what different types of financial firms could do.
In the last decade, those limits were relaxed, so many current financial firms have divisions that handle the different functions that were previously required to be separate.
Oversimplifying, the three primary types of financial firms were:
Commercial Banks/Trust Companies
Investment Banks/Brokers
Insurance Companies
Commercial Banks/Trust Companies
Examples: Chase Manhattan Bank, Citibank, Bankers Trust, J.P. Morgan
Commercial Banks generally have as their primary business the taking of deposits and the making of loans. They also often function as Trust Companies, which can serve as trustees of personal or business trusts.
For instance, if you wanted to create a trust for your children, you could deposit money or securities with the trust department of a commercial bank under a trust agreement, and the trust officers of the bank would manage the funds and pay the beneficiaries under the terms of the trust agreement. Also, an investment bank could create a mutual fund organized as a business trust, and the bank could serve as trustee and custodian of the securities in the fund.
Investment Banks/Brokers
Examples: Merrill Lynch, Morgan Stanley, Goldman Sachs
One primary function of Investment Banks/Brokers is that of Stockbroker. Stockbroker will arrange for the purchase or sale of stocks, bonds and other securities for people. They will also hold securities for people in brokerage accounts.
Another primary function is that of Underwriter. If a company wishes to issue securities to the public, it will arrange with an investment bank to agree to distribute the securities to the market.
A related function is providing securities advice to individuals and businesses. A full-service stockbroker will advise individuals on how they should structure their investments. An investment bank will advise companies on what securities that they should issue.
Yet another function of investment banks/brokers is trading for their own accounts. They buy and sell securities in the hopes of making money for themselves.
Insurance Companies
Examples: The Travellers, Metropolitan Life, Aetna
Insurance Companies take premiums, invest the premiums, and make payments on the occurance of specified events (death, fire, accident, etc.). Insurance companies, particularly life insurance companies, often will sell insurance products that have an investment component, that is to say that the idea is that the insured will get dividends or returns before the payout on death.
The combinations
Each of these companies has the function of taking money from customers and giving them a dividend/interest return. There are a variety of benefits and risks in investing in any of them (tax issues, deposit insurance, growth, etc.). Because they performed similar functions and often had competing financial products, over the last decade the laws separating them have crumbled, resulting in combinations like Travellers/Citigroup.
Even within the prior categories, companies concentrated on different aspects of their businesses. For instance, Merrill Lynch has historically concentrated on retail brokerage to individuals while Goldman Sachs has concentrated on investment banking to companies. Berkshire Hathaway, Warren Buffett’s company, is well known for its prowess in investing in companies, but it is actually organized as an insurance company, while other insurance companies concentrate on the traditional insurance business.
Of the business that you listed, the one that does not fit into one or more of these categories is aricewaterhouseCoopers, an accounting firm. accounting firms have a primary business of reporting, auditing and certifying the financial results of companies, but with other businesses (which often overwhelm the primary auditing businesses) of tax advice, business consulting, computer consulting, and sometimes securities sales.