You can also do target date funds. Each one indicates the projected year you expect to retire. As you get older, it shifts more to safer investments like bonds. The idea is invest in the stock market when you are young and don’t expect to use the money soon. You are able to hold through downturns in the market and returns have historically always trended up despite the occasional drops. When you are near retirement and expect to be using the money you can’t always afford to wait it out so you should invest in things that are more stable but have lower returns like bonds. Target dates have slightly higher fees and you should always check what the fees are before you invest, but they are very set it and forget it.