PBP is sort of a cross between a traffic generator and a multi-level marketing scheme, only without the threats that MLM traditionally entails. You’re not absolutely required to sign up under someone, though the program does cost money on a monthly basis. You’re granted access to traffic generation tools, as well as other promotional information and training. The MLM comes in with their referral commissions, which many people use more than the marketing tools themselves. There’s a sizable commission for enrolling new members, as well as seeing them succeed.
Not all web traffic is welcomed. Some companies offer advertising schemes that, in return for increased web traffic (visitors), pay for screen space on the site. There is also "fake traffic", which is bot traffic generated by a third party. This type of traffic can damage a website's reputation, its visibility on Google, and overall domain authority.