While saving means putting aside money you don't spend, investing means buying assets that have the potential to provide a reasonable rate of return. If you save a ton of money but keep cash under your mattress, that money loses value over time thanks to inflation. If you want your nest egg to grow, you need to invest. This doesn't mean sinking your savings into lottery tickets, even if you have the potential to turn a $1 investment into millions. You need to take calculated risks.