Because 2Checkout exclusively sells software and digital products, it is best suited for established influencers whose target audience is interested in buying products in this niche. But while you won’t find any physical products for sale, 2Checkout is probably the market leader in selling software of every type, including very specific use case items (like software that can convert Microsoft Word documents to PDF, for instance).
Some advertisers offer multi-tier programs that distribute commission into a hierarchical referral network of sign-ups and sub-partners. In practical terms, publisher "A" signs up to the program with an advertiser and gets rewarded for the agreed activity conducted by a referred visitor. If publisher "A" attracts publishers "B" and "C" to sign up for the same program using his sign-up code, all future activities performed by publishers "B" and "C" will result in additional commission (at a lower rate) for publisher "A".