To make sense of "welcome free spins", start with how the offer is built. A welcome offer is rarely one bonus. It is usually a package spread across several deposits, each with its own match percentage, ceiling and conditions, and sometimes with free spins attached. The headline adds the parts together, which makes the whole look larger than any single step. Taking the package apart shows what each deposit actually earns and what it asks in return.
A match bonus adds a percentage of the deposit, up to a ceiling. A hundred percent match up to a stated maximum doubles a deposit that stays under the ceiling, and adds nothing to the part above it. Higher percentages usually come with lower ceilings or heavier wagering. Comparing offers by the bonus a planned deposit would actually receive, instead of the largest figure in the banner, keeps the comparison honest and often reverses the order of two offers.
Reload offers return after the welcome package, often weekly, with smaller matches and the same kind of wagering. Whether any bonus is sticky or cashable matters as much as its size. A sticky bonus can be played with but is removed at withdrawal, so only the winnings above it can be cashed. A cashable bonus becomes part of the balance once the requirement is met. The terms name the type, sometimes under another label.
A match bonus adds a percentage of the deposit up to a stated maximum, so a full match doubles a deposit under the ceiling and adds nothing above it.
No deposit offers give credit or spins for simply registering, so casinos pair them with high wagering, a low withdrawal cap, a short deadline and one claim per household.
Some offers only apply when a box is ticked before payment, and a deposit made without opting in usually earns nothing afterwards.
Bonuses that return after the welcome package, often weekly, with smaller matches and the same kind of wagering attached.
Each tier unlocks only after the previous one is claimed, often within a set number of days from registration, and later tiers usually match smaller percentages.