What is an ETF? A beginner's guide to index funds

What is an ETF?

ETF stands for Exchange-Traded Fund. Do not let the corporate-sounding name throw you off, because the idea is actually pretty simple. An ETF is basically a big box that holds tiny slices of loads of different companies. You buy a share of the box, and just like that, you own a piece of everything inside it.

Think of it like a Spotify playlist, but for stocks. Instead of carefully picking one song (one company) and hoping it hits, you press play on a playlist that already has hundreds of songs in it. If one turns out to be a skip, it barely matters. The playlist as a whole still delivers.

Most ETFs follow something called an index. An index is just a list of companies grouped by a rule. The FTSE 100, for example, is a list of the 100 biggest companies on the London Stock Exchange. A FTSE 100 ETF automatically spreads your money across all 100 of them, sized by how big each company is. You do not pick anything. The fund just mirrors the index, end to end.

How does an ETF work?

When you buy an ETF, you are really buying a tiny share of a giant pre-built collection. The behind-the-scenes admin (actually buying all those underlying stocks, keeping them organised, handling the paperwork) is done by an asset manager. The big names you will see are Vanguard, iShares (owned by BlackRock), and HSBC. They charge a small annual fee for the service. More on that later.

Here is the clever bit: most ETFs do not have a fund manager trying to pick winners. They just follow the rules of the index. If a company gets big enough to break into the FTSE 100, the fund adds it automatically. If another one falls out, it gets dropped. This is called passive investing, and because there is no expensive expert getting paid to predict the future, the fees are way lower than active funds.

Because ETFs trade on a stock exchange (yes, that is literally the "exchange-traded" part of the name), the price moves throughout the day. Regular index funds only get priced once daily. For a long-term investor though, that gap is mostly irrelevant. You are not day-trading, you are letting it grow.

What happens to dividends?

Some of the companies inside your ETF will pay dividends, which are small cash payouts to the people who own their shares. With an ETF, those dividends get handled in one of two ways. An accumulating (Acc) ETF reinvests them automatically, so your money grows faster without you lifting a finger. A distributing (Dist) ETF pays them out to you as cash, which you can then spend or reinvest yourself. If you are investing for the long haul and just want it to grow, Acc is usually the easier life.

Types of ETF

There is an ETF for pretty much every corner of the financial world. Most beginners stick to a broad market ETF and call it a day, but it is useful to know what else is out there, even just to recognise the buzzwords when you see them.

Why diversification matters

Diversification is probably the most overused word in investing, but it actually matters. The idea is dead simple: spread your money across loads of different investments, so no single one can wreck you if it tanks.

Imagine you sink everything into one high street retailer. Bad sales year, store closures, full-on collapse: your money goes down with it. Now imagine instead that your money is split across 1,600 companies in 50 countries. If one of them goes under, it might represent 0.06% of your total investment. You would barely blink.

This is exactly what a global ETF does for you. The chart below shows roughly how a typical global ETF spreads your money across the world, based on the size of each region's stock market.

The US takes the biggest slice because American companies are, by far, the most valuable in the world right now. That means you automatically own a chunk of Apple, Microsoft, Amazon, Nvidia and everyone else, without ever having to pick one yourself.

And here is the magic: as some regions or companies grow and others shrink, the index rebalances automatically. You do not have to do a thing. It is investing on autopilot, by design.

Understanding ETF fees, and why they matter more than you think

Every ETF charges a small annual fee called the Ongoing Charge Figure (OCF), sometimes also called the Total Expense Ratio (TER). It is a percentage of however much you have invested, and the best part is you never see it leave your account. It is quietly taken out of the fund itself.

For a cheap global ETF, the OCF is usually somewhere between 0.07% and 0.20% per year. Sounds like absolutely nothing. But over 10, 20, 30 years, even a tiny fee difference quietly nibbles away at your returns, because the fee gets charged every year, on a smaller balance, which then grows by less, and so on. Compounding works in both directions.

The chart below shows the damage in action. Slide the inputs around and see what a "small" fee actually costs your future self over time.

That gap is not bad luck, it is pure fee leakage. Money you would otherwise keep. For an active fund to justify its higher cost, it has to consistently beat the market by more than the extra fee. Decades of research show most do not. That is the whole argument for cheap index ETFs in one paragraph.

ETF vs active fund: what is the difference?

Underneath the jargon, this is really an argument between two ways of thinking. Passive investing (most ETFs) says: trying to consistently beat the market is genuinely hard, so just match the market for the lowest possible fee and call it a win. Active investing says: with the right research and a smart manager, you can beat the market, and the higher fees are worth paying.

Both sides have their points. But the receipts tend to favour passive. Across decades of studies, most active funds end up underperforming their benchmark over 10+ years, especially once you take fees into account.

How to buy an ETF in the UK

Buying an ETF in the UK is honestly easier than people make it sound. You need an investment account on a platform that lets you buy them, and most do. Ideally, do it inside a Stocks and Shares ISA, so any gains and dividends stay completely tax-free.

1. 1

   Open a Stocks and Shares ISA or general investment account

   Popular UK platforms include Vanguard, InvestEngine, Hargreaves Lansdown, and Trading 212. Compare the platform fees: some take a percentage of your portfolio, others charge a flat monthly amount. If you are starting small, percentage-based fees are usually the cheaper option.

2. 2

   Search for the ETF you want

   You can search by name or by ticker, which is the short code each fund has on the stock exchange. iShares' big FTSE 100 ETF, for example, trades under the ticker "ISF". Most platforms let you filter by region, index, or provider to help you narrow it down.

3. 3

   Check the key fund details

   Before you click buy, check three things: the OCF (annual fee), the fund size (bigger funds tend to be more stable), and whether it is Acc or Dist. The Key Investor Information Document (KIID) is a one-pager available on the platform or the provider's site, and it covers all of this without the jargon.

4. 4

   Place your order

   You can either buy a set number of units at the current market price, or (on platforms that allow it) invest a fixed amount in pounds and let the platform work out the units. The second option is usually easier when you are starting out.

5. 5

   Set up a regular investment if you can

   Most platforms let you set up an automatic monthly purchase, sometimes called a regular investing plan. This is called pound-cost averaging: you buy more units when prices are low, fewer when prices are high, which smooths out the bumps and removes the temptation to try and time the market.

Frequently asked questions