The first ETF (VTI) gives you exposure to basically the entire U.S. stock market by investing in over 4,000 stocks. The second ETF (VXUS) fills in the rest of the world with exposure to over 6,000 global stocks outside the U.S. (the top six countries represented, in order, are Japan, the UK, Canada, France, Germany, and China). While the stock market is riddled with uncertainty, certain tried-and-true principles can help investors boost their chances for long-term success. Here are 10 fundamental concepts every investor should know: Some investors lock in profits by selling their appreciated investments, An investor can lose sight of long-term trends. If you want to consider a really long-term perspective, here's an interesting fact: Since 1871, the stock market has never been in a long-term downward trend. A line drawn through the chart showing the average trend goes straight up at almost a 45-degree angle.