A Welcome Deposit Bonus is a promotional offer provided by online casinos and betting sites to attract new players. When a user makes their first deposit, the site matches a percentage of that amount, often up to a specified limit, effectively boosting the player's initial bankroll. This bonus allows newcomers to explore the platform and try out various games with extra funds, enhancing their gaming experience. However, it's essential to read the terms and conditions, as wagering requirements and restrictions may apply before withdrawing any winnings derived from the bonus.