A sticky casino bonus is a free none-cashable bonus, it is also known as a phantom bonus.
These types of casino bonuses and promotions will add free chips money to your casino account - you can use that money to play at the casino, try it out and even win some cash, however you cannot cash out the bonus itself, you can only cash out your winnings(deducting the free bonus).
Sticky bonuses are great for helping you to increase your winning odds, Once you have a sticky bonus and you understand the rules and limitations around it, you can make use of that bonus and make good money.
Sticky Bonuses are a rather unique type of bonuses in the world of Online Casinos. The gist is that these are bonuses which are given to players merely as a wagering vessel. Where these bonuses get their name from is from the fact that they do practically "stick" in your Bankroll, since you cannot withdraw them under any circumstances.
These bonuses are meant to give players a head start in gambling in an Online Casino, because as they start playing, they already have an amount in their Bankroll, without any need for depositing any cash themselves. They can use this money to wager, and they can withdraw all wins made using this sticky sum, but they cannot withdraw the original amount of the sticky bonus. This is also a reason why Sticky Bonuses are sometimes jokingly called "Phantom Bonuses".
While the non-cashable aspect of Sticky Bonuses can justifiably deter players, it should be kept in mind that Sticky Bonuses tend to be composed of larger sums than other cashable bonuses. Wagering requirements are also lower and less harsh like in other bonuses, and the choice of games on which you can wager with the Sticky Bonus is usually much wider.