A compound interest calculator will give you an idea of how your savings and investments can grow over time.
Compound interest is when interest is applied to a principle amount at one point, with the interest being added to the original amount, and then the interest is calculated again at the next time period (such as monthly, though some accounts do count daily).
Leaving your interest in your savings amount, rather than withdrawing it or sending it somewhere else, generally helps your sum of money grow faster!