A bonus and a promotion from an online casino are interchangeable terms that refer to the special offers an online casino provides players who sign up with their site during a specific period of time, meet a specific depositing requirement, reach a playing requirement, or play a certain game or type of game for a certain amount of time.
Bonuses and promotions can come in the form of:
Free money you can use to play any game or certain games as outlined in the bonus/promotion terms and conditions.
Free plays/spins on certain games as outlined in the terms and conditions.
A deposit match after reaching a specific deposit amount.
An amount of time to play games for free, as outlined in the terms and conditions.