The percentage means that the company pays out a percentage of the advertising revenue they receive. Payment rates will therefore fluctuate depending on how much advertising they received. The amount the program will pay you for the people you get to sign up. When you recruit others, give them this ID, and make sure they sign up using it. That way, they'll get paid, and you'll get paid for recruiting them.
Most programs have different rates for different levels of referrals.
You also get paid for them, but usually at a lower rate. This is how far down the referral chain you get paid. AllAdvantage has 4 levels, ClickDough has 8. This is how these programs can really pay out large sums. Of course, through referrals, you have the opportunity to make a lot more.