The main bonus types
A welcome bonus matches a percentage of your first deposit, often 100% up to a cap, sometimes across several deposits. A no-deposit bonus gives a small amount with no purchase but almost always has the harshest wagering and a low maximum cashout. Reload bonuses target existing players with smaller matches.
Cashback returns a percentage of net losses over a period and is usually the most honest offer type, because low-wagering or wager-free cashback has real, calculable value. Free spins are usually bundled with a deposit match and tied to specific slots at a fixed spin value.