What is the difference between index funds and ETFs?

Related questions

1. What is the QQQ?
2. What is Invesco QQQ Trust Series 1?
3. Is QQQ cash settled?
4. What is Nasdaq ETF?
5. What is the difference between American and European options?
6. How many stocks make up the S&P 500?
7. Is QQQ a mutual fund?
8. How often does Vanguard ETF pay dividends?
9. What are ETF investments?
10. What stocks make up the Nasdaq?

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