You can receive bonus money through various promotions, e.g. through deposit bonuses. As a rule, the bonus money is calculated as a percentage of the deposit amount. With a 100% bonus, for example, this means that if you deposit € 100, you will receive an additional € 100 in bonus money. The balance available to play with is then € 200.
Tip: By fulfilling the wagering requirements, bonus money is converted into real money and is then also available for withdrawal. You can check the current status on the bonus page.