If you have ever wondered what smart investors quietly do with their money while everyone else chases hot stocks, the answer is often the same: index funds. Warren Buffett famously recommended them. Millions of everyday people have quietly built wealth through them. And yet, a surprising number of people still have no idea what they are.
This guide breaks it all down in plain English, from what an index fund actually is to whether you should start investing in one today.
What Is an Index Fund?
An index fund is a type of investment that tracks a specific market index, such as the S&P 500, the Nasdaq-100, or the total US stock market. Instead of a fund manager handpicking stocks, an index fund simply buys all (or most of) the stocks in a given index in the same proportions they appear.
Think of it this way: instead of betting on one racehorse, you are buying a small stake in every horse in the race. Some will lose, but enough will win that you come out ahead over time.
How Do Index Funds Work?
When you invest $1,000 in an S&P 500 index fund, your money is spread across 500 of the largest US companies, including Apple, Microsoft, Amazon, Nvidia, and more. As those companies grow, your investment grows with them.
Passive management: Because index funds are not actively managed, their fees are dramatically lower than traditional mutual funds. Many charge as little as 0.03% annually.
Diversification: One fund gives you exposure to hundreds of companies across multiple industries, reducing your risk significantly.
Consistent returns: The S&P 500 has historically returned an average of 10% per year over the long term.
Index Funds vs Actively Managed Funds
Research consistently shows that over a 10-year period, more than 90% of actively managed funds underperform their benchmark index. In other words, the professionals rarely beat the market — and they charge you more for the privilege of trying.
Pro Tip: Even the world’s most successful investors, including Warren Buffett, have publicly endorsed low-cost index funds as the best option for most everyday investors.
Best Index Funds to Consider in 2026
For Beginners
- Vanguard S&P 500 ETF (VOO) — 0.03% expense ratio
- Fidelity ZERO Total Market Index Fund (FZROX) — 0.00% expense ratio
- iShares Core S&P 500 ETF (IVV) — 0.03% expense ratio
For Broader Diversification
- Vanguard Total World Stock ETF (VT) — covers US and international markets
- Fidelity International Index Fund (FSPSX) — international exposure
Should You Invest in an Index Fund in 2026?
The short answer is yes, for most people. Here is why:
- You do not need to pick stocks or time the market.
- The fees are incredibly low, meaning more of your money compounds over time.
- They are tax-efficient, especially in a Roth IRA or 401(k).
- Historical data strongly supports long-term growth.
The only situations where index funds may not be the perfect fit are if you need access to your money within the next 1 to 3 years, or if you are actively trying to beat the market with higher risk tolerance. For everyone else, they are a cornerstone of any smart investment strategy.
How to Start Investing in an Index Fund Today
- Open a brokerage account on platforms like Fidelity, Vanguard, or Charles Schwab (all free).
- If your employer offers a 401(k), check if index fund options are available — most are.
- Choose a broad market fund like VOO or FZROX to start.
- Set up automatic monthly contributions, even $50 counts.
- Do not check it every day. Let it grow.
Key Takeaway: Index funds are the single most accessible, proven, and low-cost way for beginners to start building long-term wealth. If you are not investing yet, there is no better place to start.
The best time to invest was 10 years ago. The second best time is today.
