Investing

What Is an ETF and How Index Funds Work

What is an ETF? Learn how ETFs and index funds let you buy hundreds of companies at once, with simple examples and the fees to watch for.

By the Euphoria team · 2026-07-17 · 6 min read

The problem an ETF solves

Imagine you want to invest in companies, but you have no idea which single one will do well. Picking one stock is a bit like betting on one horse. If it wins, great. If it stumbles, your money stumbles with it. That is a lot of pressure to guess right.

An ETF fixes this by letting you buy a little slice of many companies at once, in a single purchase. ETF stands for exchange traded fund. Break that name down and it is not scary at all. It is a fund, meaning a basket that holds lots of investments, and it is exchange traded, meaning you can buy and sell it during the day just like a normal stock.

So instead of betting on one horse, you get a tiny piece of the whole field in one move.

What is actually inside a fund

A fund is just a pool. Many people put money in, and that combined pool buys a big collection of investments. When you buy one share of the fund, you own a small piece of everything the pool holds.

Say a fund holds shares of 500 different companies. When you buy one share of that fund, your money is spread across all 500. If a few of them have a rough year, the others can balance it out. This spreading of money across many things is called diversification, and it is one of the oldest ideas in investing. It simply means not putting all your eggs in one basket.

One purchase, hundreds of companies. That is the quiet magic of a fund.

Index funds, explained simply

You will hear the words ETF and index fund used close together, so let us untangle them.

An index is just a list that tracks a group of companies to measure how a chunk of the market is doing. One famous index follows 500 large companies in the United States. When the news says the market went up or down, they are often talking about an index like this.

An index fund is a fund that quietly copies one of those lists. If the index holds 500 companies, the index fund tries to hold the same 500 in the same proportions. It is not trying to be clever or beat the market. It just tries to match it.

Many ETFs are index funds under the hood. The difference is mostly about how you buy them. An ETF trades throughout the day like a stock, while some other index funds only settle their price once a day after the market closes. For a long term investor, that timing detail barely matters.

Active vs passive, and why fees matter

There are two broad styles of fund, and the difference shows up in what you pay.

An active fund pays a manager to hand pick investments and try to beat the market. All that effort costs money, so active funds usually charge higher fees.

A passive fund, like most index funds, just copies a list. There is far less work involved, so the fees are usually much lower. That fee is called an expense ratio, and it is the yearly slice the fund takes to run itself.

Here is why a small number matters more than it looks. Say you have $10,000 invested.

• A fund with a 1 percent expense ratio charges 1 percent of $10,000, which is $100 a year.
• A fund with a 0.05 percent expense ratio charges 0.05 percent of $10,000, which is $5 a year.

That is a $95 gap every single year for what can be a nearly identical basket of companies. Over decades, and as your balance grows, that gap quietly compounds into a serious amount. This is a big reason many people gravitate toward low cost index funds.

What returns actually look like

A fair question is what you get for your money. Nobody can promise a number, and anyone who does is not being honest. Markets go up in some years and down in others.

What we can say is how the math works. If a fund grows 8 percent in a year and you have $1,000 in it, that is 8 percent of $1,000, which is $80 of growth, leaving you with $1,080. The next year, if it grows again, you earn on the larger amount, not just your original $1,000. That is compounding doing its quiet work inside the fund.

The catch is that this only tends to play out over long stretches. In any single year the fund could fall instead of rise. That is exactly why funds are usually a tool for money you will not need for many years, not for cash you might want next month.

Things to know before you buy

A few honest points to keep in your back pocket:

• A fund can still lose value. Diversification lowers the risk of one company sinking you, but it does not remove the risk of the whole market dropping.
• Lower fees are one of the few advantages you can actually control, so it is worth checking the expense ratio.
• Funds reward patience. The people who do well usually buy steadily and leave it alone, rather than jumping in and out.

None of this is a recommendation to buy any particular thing. It is just how the machinery works, so you can make your own call with clear eyes.

Why this matters for you

Funds took something that used to feel locked behind a wall, owning a piece of hundreds of companies, and made it simple enough for a beginner to understand in an afternoon. You do not need to be a stock picking genius. You just need to understand the basket you are buying and the fee you are paying for it.

On Euphoria you can build a pretend basket of companies in interactive lessons and use paper trading to watch how a fund would move over time, all without risking a single real dollar, so the idea clicks before you ever open a real account.