Media - Same as affilate. A website owner or publisher who earns commissions for referring customers to advertisers.
Merchants - Same as advertisers. Companies or people with products, goods, or services to sell who pay other people to tell potential customers about their companies, products, and services.
Multi-Tier Program - Similar to Two-Tier Programs, except the tracking also accounts for any affiliates recruited through several more tiers, similar to multi-level-marketing.