Stocks, Bonds, ETFs, and CDs: A Plain-Language Breakdown of Common Investment Types

When you buy a stock (also called a share or equity), you're purchasing a small ownership stake in a publicly traded company. If the company grows and becomes more profitable, the value of your shares can rise. Some companies also pay dividends — periodic cash distributions from profits — which can provide income alongside any price appreciation.

The tradeoff is volatility. Stock prices can rise and fall dramatically based on company performance, economic conditions, investor sentiment, and many other factors. Individual stocks carry concentration risk: if you invest heavily in one company and it struggles, your portfolio can take a serious hit. Stocks are generally considered long-term investments because short-term price swings can be severe.

A bond is essentially a loan you extend to a borrower — typically a corporation or a government entity. In return, the borrower agrees to pay you a fixed rate of interest (called the coupon) over a set period, then return your original investment (the principal) when the bond matures.

Bonds are generally considered lower-risk than stocks, though they're not risk-free. Bond prices move inversely with interest rates — when rates rise, existing bond prices typically fall. There's also credit risk: if the issuer defaults, you may not get all your money back. U.S. Treasury bonds are backed by the federal government and are among the lowest-risk fixed-income options available, while corporate bonds vary in risk depending on the issuer's financial health.

An exchange-traded fund (ETF) pools money from many investors to buy a collection of securities — often tracking a market index like the S&P 500. When you buy one share of an ETF, you're effectively buying a tiny slice of every security inside that fund, which spreads your risk across many companies or asset classes at once.

ETFs trade on stock exchanges throughout the day, just like individual stocks, making them flexible. They also tend to carry lower costs than actively managed funds, because many simply track an index rather than relying on a team of analysts to pick investments. If you'd like to understand how index-tracking ETFs compare to actively managed approaches, our comparison of index funds and actively managed funds goes deeper on that topic.

A certificate of deposit (CD) is offered by banks and credit unions. You deposit a set amount of money for a fixed term — anywhere from a few months to several years — and in return you receive a guaranteed interest rate. At the end of the term (called maturity), you get your original deposit plus the interest earned.

CDs held at federally insured institutions are covered by FDIC insurance (up to applicable limits), making them one of the lower-risk ways to earn a return on cash savings. The main limitation is liquidity: withdrawing money before the CD matures typically triggers a penalty. CDs are generally better suited to money you know you won't need in the near term, rather than funds you may need to access quickly.

While not always in the headline alongside the other four, mutual funds appear frequently in retirement accounts like 401(k)s and are worth understanding. Like ETFs, mutual funds pool investor money to buy a diversified basket of securities. The key differences: mutual funds are priced once per day (after markets close) rather than throughout the trading day, and many are actively managed, meaning a portfolio manager decides which securities to buy and sell.

Active management can come with higher fees, often expressed as an expense ratio — the annual percentage of your investment deducted to cover fund costs. Higher fees don't automatically mean better performance; research has consistently shown that most actively managed funds underperform their benchmark index over long periods, especially after fees. That said, some investors prefer the human judgment involved in active management, particularly for specialized or less-efficient markets.