When you want to invest but don't want to pick individual stocks and bonds yourself, you can turn to investment companies. These firms pool money from many people and invest it in a broad range of securities like stocks, bonds, and other assets. This gives individual investors access to diversified, professionally managed portfolios.

The entire industry is shaped by a key piece of legislation: the Investment Company Act of 1940. This law was enacted to protect investors by setting standards for how these companies operate, what they must disclose, and how they are structured. It classifies investment companies into three main types: open-end funds (mutual funds), closed-end funds, and unit investment trusts (UITs). A popular modern product, the exchange-traded fund (ETF), is a close relative with its own unique features.

Mutual funds are the most common type of investment company. They are technically known as open-end funds because they can create new shares for new investors and buy back shares from those who want to sell. Think of it like a collective investment pot. Many investors contribute money, and a professional fund manager uses that pool of capital to buy a variety of securities.

Each investor owns shares that represent a portion of the fund's holdings. The price of a mutual fund share is called its Net Asset Value (NAV). It's calculated once per day after the market closes by taking the total value of all the securities in the portfolio, subtracting any liabilities, and dividing by the number of shares outstanding. All purchases and sales happen at that day's NAV.

Mutual funds have different objectives. Some aim for long-term growth by investing in stocks (equity funds). Others seek steady income by investing in bonds (fixed-income funds). Money market funds focus on safety and liquidity by holding short-term debt. Balanced funds mix stocks and bonds to offer both growth and income.

This pooling structure allows you to achieve diversification more easily and cheaply than by buying all the individual securities yourself.

While mutual funds are popular, they aren't the only option. Other structures offer different features for different needs.

Unit Investment Trusts (UITs) A UIT is a more passive investment. It buys a fixed portfolio of securities—usually stocks or bonds—and holds them for a set period. Once the portfolio is created, it doesn't change. Because they are not actively managed, UITs generally have lower management fees. At the end of the trust's life, the assets are sold and the proceeds are paid out to the investors. UITs are popular with investors who want a specific, unmanaged collection of assets for a predetermined time.

Exchange-Traded Funds (ETFs) ETFs are a hybrid of mutual funds and stocks. Like a mutual fund, an ETF holds a basket of securities, often designed to track a specific index like the S&P 500. But like a stock, ETF shares are traded on an exchange throughout the day at market-determined prices. This provides the diversification of a mutual fund with the trading flexibility of a stock. Investors can buy and sell ETFs anytime the market is open, use advanced order types, and even sell them short. This intraday trading is a key advantage over mutual funds, which only trade once per day.

Understanding these different structures is crucial. An investor's choice depends on their goals, whether they prioritize active management, trading flexibility, or a fixed, passive portfolio.

Time to check your understanding of these core products.

Each of these products—mutual funds, closed-end funds, UITs, and ETFs—offers a different way to access a diversified portfolio, all under the watchful eye of the Investment Company Act of 1940.