A 100% bonus deposit is a promotional offer commonly used by online casinos and betting sites to attract new players. When a user makes their first deposit, the platform matches it with an equal amount in bonus funds, effectively doubling the player's initial bankroll. For example, if a player deposits $100, they receive an additional $100 in bonus money, allowing for more extensive gameplay and increased chances of winning. However, it's essential to review the terms and conditions, as these bonuses often come with wagering requirements that must be met before withdrawals can be made.