The general advice is not to park one’s money in a savings account. The general advice is to park one’s money in an index fund. Let’s say one buys AAPL stock

The general advice is not to park one’s money in a savings account. The general advice is to park one’s money in an index fund. Let’s say one buys AAPL stock or the Vanguard Total Stock Market ETF – in what way is that to invest in fiat?