This sort of bonus means that a player gets a refund of some money used in the betting process. It may be an assurance that one is refunded if they lose the first bet, or reimbursed the service charge when betting. The guarantee allows the player to bet without risk of loss for some time.
Luxembourg is undoubtedly one of the smallest countries in Europe, but politically, it is more significant than its size, housing several EU institutions and several powerful banks. While gambling is illegal in Luxembourg, online casinos are in practice tolerated. Locals can safely play in international live online casinos without fear of sanctions.