What is index fund investing and why do people recommend it?

Index fund investing means buying a fund that tracks a market index like the S&P 500, which holds shares of hundreds of companies proportionally. Instead of picking individual stocks, you own a small slice of the entire market or a broad sector of it. People recommend it for several reasons. First, it's extremely low cost since there's no active manager making decisions, so fees are minimal. Second, research consistently shows that most actively managed funds fail to beat the market over long periods, so passive index investing tends to outperform them after fees. Third, it provides instant diversification, reducing the risk of any single company collapsing and wiping out your investment. It's considered a reliable, simple long-term wealth-building strategy for ordinary investors.