A sign-up bonus refers to an offer that casino gives to new customers once they sign up on their site. Casinos use these bonuses to attract new customers and provide them with some funds to start betting. Sign-up bonuses are not withdraw-able and should be used within a timelimit, depending on the casino.
The Grand Duchy of Luxembourg is in Western Europe. It is a mix of French and German cultures, and is a small landlocked country, home to the European Court of Justice. Mobile online gambling is known to be illegal for residents, but they are rarely prosecuted, and the local government is unwilling to block international online casinos.