Most of them give you a match bonus, where you make a deposit and receive a percentage of your deposit back as free bonus money. If it’s a 100% match bonus of up to $100, for example, and you deposit $100, you will receive a free $100 in bonus money on top of your deposit – you will end up with $200 in total to play with.
Some offers reward you with free spins as well. If you receive free spins from a welcome bonus, you will usually get a set number of them and they will either be usable on all the casino’s slots or a select few.
A lot of welcome bonuses reward you for making your first deposit. at some casinos, you will continue to receive bonuses for several deposit after your first.