Typically agencies who either send you leads or close business on your behalf. They may also run the client's program on your software and charge them for services. Also see "value added reseller"
An affiliate program is an organized system that enables affiliates to drive traffic to your properties through tracked links, and earn a cut when that traffic converts. Affiliates come in many different forms and they can include: influencers, content creators, publications, membership associations, and technology vendors.