It has been conventional wisdom for the last 50 years that if you are a long-term investor, your best return will be in stocks. Almost every financial advisor will tell a 30-year-old to put upwards of 90% of their portfolio in equities.
Most people above median wealth have a substantial allocation of their liquid portfolio in the stock market. Some people pick individual issues Apple, GE, Wal-Mart, etc. and some invest in managed mutual funds Fidelity, say, while others invest in index funds the Vanguard S&P 500 fund, for instance.
Stocks are less than 10% of my portfolio. This is a long article read time is going to be at least 12 minutes but I implore you to read it in full.
“Never invest in a business you cannot understand.” – Warren Buffett