Compound Interest
Compound interest is interest earned on both your original money and the interest it has already generated. Over time this creates a snowball effect where growth accelerates the longer you stay invested. It is the core reason starting to save early matters so much.
Example
$10,000 invested at 7% compounded annually grows to about $19,672 in 10 years and $76,123 in 30 years — without adding another dollar.