J.V.
Yes, you can lose money. In fact, there was that big controversy that the safe bonds lost tons of money.
Investing in stocks can be better than a savings account because there is the chance you can make a lot more money. Savings account have very low interest rates. Stocks? They can earn anywhere from 0-30% a year. They can also lose the same.
If you put all the money in their Index fund, you should be OK. It's about the long run, what happens over 15-20 years, not what happens today. So, when the fund loses money, you say to yourself "good, I'm buying stocks cheaper now." In fact, when the stock market crashed and burned two years ago, hubby and I added tons of money to our daughter's Bright start account. Instead of worrying about losing half our money, we just thought about our cheap the stock where.