In short: a stock is a small piece of one company; an index ETF holds pieces of hundreds or thousands of companies at once. Spreading makes a disappointment at one company count for little, but it does not protect you against a fall of the whole market. Long-run research on American stocks found that most single stocks did worse than short-term government bills over their lifetime, while a small group drove almost all the gains.
Many beginners ask: why an ETF and not just a few stocks? This guide explains what a stock is, what an ETF changes and why the risk of one company matters. You get no advice; you see what each choice means, so you can choose for yourself.
What is a stock?
A stock is a small piece of ownership in a company. Companies issue stocks to raise money, for example to grow. Whoever buys one becomes a part-owner, a shareholder. Stocks are bought and sold on an exchange, through a broker, and the price, the share price, changes throughout the day as buyers and sellers keep agreeing on what the company is worth.
You can earn from a stock in two ways. The share price can rise after you buy, so your piece is worth more; it can also fall. And some companies pay part of their profit to shareholders as a dividend; not every company does, and a company can stop. In the extreme case a company fails, its stock becomes worthless and what you put into it is gone.
The full answer, with what you own, how the price is set, dividends, splits and what happens when a company fails, is on What is a stock?
What an ETF changes
An ETF is a fund that holds stocks of many companies at once, often all the companies in an index. One purchase gives you a small piece of each. How many that is depends on the index:
- The MSCI World index held 1,280 companies in August 2026, and the ten largest together weighed 26.61% (MSCI factsheet).
- The FTSE All-World index held 4,264 companies on 31 August 2026, and the ten largest together weighed 23.73% (FTSE Russell factsheet).
Those last numbers matter too: spreading over a thousand companies does not mean every company counts equally. In both indexes about a quarter of the money sits in ten companies, so a broad ETF still leans on its largest holdings.
The risk of a single company
A company can disappoint for reasons that only affect that company: a product that does not catch on, a new competitor, a mistake by management. Its share price can then fall a lot while other companies do well. When much of your money is in that one company, this is called concentration risk.
An example with a made-up company shows what spreading does. You have €1,000. Company X halves in value.
- If all €1,000 is in Company X stock, you lose €500.
- If Company X makes up 0.5% of an ETF and the other companies stay where they are, the ETF falls 0.25%: €2.50 on your €1,000.
It works the other way round as well: if Company X doubles, that counts for little in the ETF. Spreading smooths out both the bad and the good surprises.
Why that matters becomes clear from long-run research. Hendrik Bessembinder studied nearly 26,000 American stocks traded since 1926. Over their lifetime, 58% of them did worse than one-month US Treasury bills, and just 1,092 companies, 4.3% of the total, accounted for all the net wealth the stock market created (Bessembinder, “Do stocks outperform Treasury bills?”, Journal of Financial Economics, 2018; summary by Arizona State University, both checked 19 October 2026). Someone who picks a handful of stocks has a real chance of missing that small group; an index fund holds it by design. This is past research on one market and says nothing certain about the future.
What spreading does not do
Spreading reduces the risk of one company, not the risk of the market as a whole. When almost all prices fall at the same time, for example in an economic setback, a broad ETF falls too. The dot-com bubble shows how deep and long such a fall can be, and the market crash simulator lets you see what one would do to your own amounts.
Side by side
- Number of companies: one per stock; from about a thousand to several thousand in a broad index ETF.
- Research: with single stocks you choose each company and follow its news; with an ETF you choose a fund and it follows its index.
- Costs: a stock has no yearly fund costs, but every purchase and sale costs something, and spreading over many stocks means many orders; an ETF has a yearly TER as well as order costs. Worked out in euros on What does buying stocks cost?
- Outliers: a single stock can rise or fall much further than a broad fund.
Questions to ask yourself
- How much time do I want to spend following companies?
- What share of my money would be in one company, and what would I do if it were worth half for a while?
- How long can I do without this money?
There is no right or wrong answer; it depends on your goal, your time and how many ups and downs you can take. A first route for beginners is at Getting started, and the ETF Calculator shows what costs do over the years.
Frequently asked questions
Can a stock go to zero?
Yes. If a company fails, its shares can become worthless. A broad index fund does not fail in the same way because it holds many companies, but it can still fall together with the market.
Is buying stocks the same as investing in an ETF?
No. A stock is a piece of one company. An ETF is a fund that holds pieces of many; see the comparison above.
This is general information, not tax or investment advice. Investing involves risk: you can lose money, and past results are no guarantee for the future. For your own situation, consult a qualified tax adviser, a financial adviser licensed by the AFM (the Dutch financial markets authority) or the Belastingdienst.