All terms
Compound interest (Zinseszins)
The effect of earnings generating further earnings, so your wealth grows at an accelerating pace.
With compounding, earnings are not spent but reinvested. Next year, not just your starting capital but also past earnings generate new earnings, like a snowball growing as it rolls.
Example: 10,000 euros at 5 % a year grows to about 16,289 euros after 10 years and about 43,219 euros after 30 years. Wealth grows fastest in the later years.
The key ingredient is time. Starting early helps most. With stocks, returns vary from year to year, so 5 % is only an illustration.