A welcome bonus is exactly what the name implies: a bonus given to any new player at an online casino. Generally speaking, these bonuses come in the form of a deposit bonus (in the form of extra money added to your account) which you can use to play a defined selection of their games.
As you play and wager your money, you’ll clear the bonus and unlock the largest portion of the offer. The more you play, the better the bonus gets, and you can often find yourself with hundreds (even thousands) of Euros extra to play with.