The concept of affiliate programs are just easy to understand. You see those guys giving out flyers for condo spaces and houses in the suburbs? You would assume that they have places there and are just selling you the idea of buying a condo at their property or whatever but the truth is, almost none of them own any of those properties, and a good amount of them are just hired by the property provider, etc. To market these condos and houses at their behest, and in exchange for every successful sale they are given a portion of the profits tagged as commission.
The same idea works for casinos, as an affiliate you're given a link which you will send to your prospects, and each time someone registers, deposits, or gambles using your link, you either earn a point, equivalent to a certain denomination of money, or cold-hard cash.
Being affiliated to a company is quite similar to being a sales man. And it's not difficult to understand. The most tedious aspect of being an affiliate is getting people to patronize the casino. It's not simple, starting out as an affiliate, but the best aspect of it is the commission as you mentioned. And some casino keep on giving out those commissions provided the (your) affiliate still gambles with them. Attaching an affiliate link to your signature also works fine in fetching some commission. The person who introduced Op into affiliate marketing should have told him more of how it works. And it's also a nice thing to try. As it could yield a long lasting stream of income to Op, if he does the right thing.