"Adult Networks/Services" consists of domains associated with companies and vendors that specialize in offering commercial services through or to the online adult content industry. These services may consist of advertising, metrics, content aggregation, registration & billing, and age verification. Many of these adult services may have ties to the distribution of adware, spyware, and dialers.
"Adult Hosts" consists of large hosting networks that specialize in hosting large numbers of web sites devoted to adult content. Many of these large hosting networks offer their own advertising and metrics services for hosted sites, and may have ties to the distribution of adware, spyware, and dialers.