Still don't quite get it? Ok, one more time.. In this model "COMPANY A" is being used to represents sites like freenotebooks.com, freeipodshuffle.com, etc. (ANY OF THE SITES OFFERING YOU A FREE PRODUCT, TO GO SIGN UP FOR AN OFFER AT ANOTHER SITE)
"COMANY B" is being used to represent sites like Blockbuster, BMG Music, USA Today, Columbia House, Cheaptrips.com. (ANY SITE THAT YOU GIVE ACTUAL BILLING INFO TO, OR SIGN UP FOR FREE TRIALS WITH)
In this model, "COMPANY A" is an Advertising Agent for "COMPANY B". "COMPANY B" pays "COMPANY A" for exposure to their services/products.
"COMPANY B" makes money when people remain customers with them. "COMPANY A" makes money by sending referrals to "COMPANY B". YOU get free stuff by signing up with "COMPANY A", and then having them refer you to "COMPANY B," and then having a given number of friends do the same.