Types of Investment Funds

An investment fund is a pool of money from many investors, run as a single basket of holdings such as stocks or bonds. Buying one share of the fund gives you a slice of everything it owns, which is how a small amount of money can become instantly diversified across hundreds or thousands of companies. Instead of researching and buying each holding yourself, you own them collectively through the fund and pay a small annual fee, the expense ratio, for the convenience.

The different types of funds are mostly variations on three things: how you buy and sell them (intraday on an exchange, or once a day at a calculated value), how the holdings are chosen (passively tracking an index, or actively picked by a manager), and who is allowed in (anyone with a brokerage account, or only accredited investors). Everything below comes back to those three axes.

An ETF, or exchange-traded fund, trades on a stock exchange throughout the day, so its price moves in real time just like a single stock. You can buy or sell whenever the market is open, place limit orders, and start with as little as one share (or a fraction of one at many brokers). Most broad ETFs are index funds with very low expense ratios, often in the 0.03% to 0.20% range.

Two features make ETFs the default choice for many investors today. First is cost: broad index ETFs are among the cheapest products in investing. Second is tax efficiency: an ETF's in-kind creation and redemption mechanism lets it limit the taxable capital gains it passes on to shareholders, which matters in a taxable account. The flip side is that ETFs trade in whole or fractional shares rather than flat dollar amounts at some brokers, and buying intraday means you watch a moving price.

A mutual fund pools money the same way an ETF does, but it does not trade on an exchange. Instead it prices once per day after the market closes, at its net asset value (NAV), the total value of its holdings divided by shares outstanding. Every order placed during the day fills at that single end-of-day price. You typically buy a flat dollar amount rather than a number of shares, which makes mutual funds a natural fit for automatic, recurring contributions.

That is exactly why mutual funds dominate workplace retirement plans like 401(k)s: the plan can sweep a fixed dollar amount from each paycheck into the fund without worrying about share prices. Mutual funds come in index and active flavors. Index mutual funds are cheap, often around 0.04%, while actively managed ones can run 0.5% to over 1% to pay for their managers. In a taxable account they also tend to distribute more capital gains than a comparable ETF.

Index fund is not a separate wrapper; it is a strategy. An index fund simply tries to mirror a market benchmark, such as the S&P 500 or the total US market, by holding the same securities in the same proportions. Because there is no manager trying to outguess the market, the cost is tiny. An index fund can be packaged as either an ETF (like VOO) or a mutual fund (a traditional index mutual fund tracking the same benchmark). So the ETF-versus-mutual-fund choice and the index-versus-active choice are separate questions.

The contrast is active management. An active fund pays a manager or team to pick holdings and time trades in an attempt to beat the benchmark, and charges more for the effort. The catch, shown repeatedly in long-run studies, is that the large majority of active funds have trailed their index after fees over time. That track record is the single biggest reason low-cost index funds have swallowed so much of the market. Our ETF vs index fund guide untangles the wrapper-versus-strategy confusion in detail.

A closed-end fund raises money once through an initial offering, issues a fixed number of shares, and then those shares trade on an exchange like a stock. The fixed share count is the defining quirk: because new shares are not continuously created or redeemed, the market price can drift above the value of the underlying holdings (a premium) or below it (a discount). Buying at a discount is part of the appeal for some investors.

Closed-end funds often focus on income, frequently use leverage (borrowing to amplify returns), and tend to carry higher fees, often 1% or more. The leverage and the discount-or-premium dynamic make them more complex and more volatile than a plain index ETF, so they are generally for investors who understand what they are buying rather than a first holding.

A money market fund holds very short-term, high-quality debt, such as Treasury bills and commercial paper, and aims to hold a stable share price of one dollar. In practice it behaves like a cash account that pays interest: you use it to park cash, hold an emergency reserve, or wait between investments, not to grow your wealth. Yields rise and fall with short-term interest rates.

A money market fund is not the same as a bank money market account, and it is not FDIC insured, though it is considered low risk. Costs are modest, typically in the 0.10% to 0.40% range. Think of it as the safe, liquid corner of a portfolio rather than an engine of returns.

A target-date fund is a single, all-in-one fund built around a retirement year, like a 2055 fund. Inside, it holds a mix of stock and bond funds, and it automatically shifts that mix toward bonds as the target date approaches, a preset path known as the glide path. You buy one fund and it handles the entire stock-and-bond allocation and rebalancing for you.

That simplicity is why target-date funds are the most common default option in 401(k) plans. The trade-off is less control and a fee that sits on top of the underlying funds, ranging from roughly 0.08% for index-based versions to 0.75% or more for actively managed ones. For a saver who wants to set it and forget it, the convenience is often worth it.

A hedge fund is a private investment pool open only to accredited and institutional investors, those who clear specific income or net-worth thresholds. Unlike public funds, hedge funds use wide-ranging strategies, including short selling, leverage, and derivatives, and they restrict when investors can pull money out, often to scheduled windows.

They are also expensive. The classic fee structure is two and twenty: 2% of assets per year plus 20% of any profits. The combination of high fees, limited access, and restricted liquidity means hedge funds are not part of most people's toolkit. For the everyday investor, low-cost public ETFs and index funds are the accessible alternative, and the mention here is for completeness rather than as a path most readers can take.

Across all these types, two distinctions drive almost every real decision. The first is ETF versus mutual fund. ETFs trade intraday, usually cost less, carry no dollar minimum beyond a share, and tend to be more tax-efficient in a taxable account. Mutual funds price once a day and let you invest flat dollar amounts automatically, which is why they anchor retirement plans. Often the same index is available in both wrappers, so the choice comes down to account type and how you contribute. Our ETF vs mutual fund guide breaks the comparison down line by line.

The second distinction is index versus active. Index funds mirror a benchmark for almost nothing; active funds pay for a manager's judgment and cost more, with a long-run record of mostly trailing the index after fees. These two distinctions are independent: you can hold an index ETF, an index mutual fund, an active ETF, or an active mutual fund. Getting clear on both is most of what fund selection requires.

Costs and details are approximate as of early 2026 and vary widely within each category; verify current figures on each provider's site before deciding. Most everyday investing happens in the first three rows, ETFs, mutual funds, and index funds, while the rest serve narrower purposes. For a concrete, category-by-category list of low-cost funds, see our best ETF in every category guide.

Knowing the types of funds is the easy part. The harder part is seeing what you actually hold once you have a few funds across a brokerage account and a 401(k): how much they overlap, what they cost together, and whether you are quietly paying active fees for index-like results. Most brokerage apps list your funds but will not explain how they relate.

That is where Walnut fits. It connects your existing brokerage through SnapTrade and lets you ask, in plain language through Claude, ChatGPT, or a built-in assistant, what types of funds you own, where they overlap, what they cost, and how each is doing against the S&P 500. It is read-only by default, and you approve any trade. Walnut is not an investment adviser; it helps you understand and act on your own portfolio rather than telling you what to buy.

Every investment fund pools money into one basket, but the types differ in how they trade, what they cost, and who can buy them. ETFs trade intraday, cost little, and are tax-efficient; mutual funds price once a day and suit automatic retirement contributions; index funds are the cheap, passive strategy that lives inside either wrapper. Closed-end, money market, target-date, and hedge funds each fill a narrower role, from cash-like safety to one-fund retirement to accredited-only strategies.

The two questions worth getting right are ETF versus mutual fund and index versus active; most everything else follows from those. From there you can dig into any specific ETF, look at an individual stock a fund holds, or explore a theme you want exposure to. Costs, holdings, and rules change over time; treat the specifics here as a starting point and confirm on each provider's site before deciding.