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.
Cuba is an emblematic Caribbean country in many ways, and despite difficult political relations with the US, it still attracts curiosity abroad. The communist regime banned all forms of gambling decades ago, and the ban includes online casinos. In practice the ban is not strictly enforced, and some international mobile casinos do accept Cuban players.